ESO W · became clear, that science and technology, as well as education, were priority areas for...

IIn early July, Finland joined ESO asthe eleventh member state, followingthe completion of the formal acces-

sion procedure. Before this event, howev-er, Finland and ESO had been in contactfor a long time. Under an agreement withSweden, Finnish astronomers had forquite a while enjoyed access to the SESTat La Silla. Finland had also been a veryactive participant in ESO’s educationalactivities since they began in 1993. Itbecame clear, that science and technology,as well as education, were priority areasfor the Finnish government.

Meanwhile, the optical astronomers inFinland had been engaged in the NordicOptical Telescope at La Palma and a con-sensus evolved that full access to ESOwould be important for the further devel-opment of Finnish astronomy as a whole.

Consequently, in September 1999, wewere approached informally by a Finnishdelegation, headed by Mirja Arajärvi, spe-cial government advisor to the Minister of

Education and Science, and exchangedpreliminary information. I was then invit-ed to Helsinki and, with MassimoTarenghi, we presented ESO and its scien-tific and technological programmes andhad a meeting with Finnish authorities,setting up the process towards formalmembership. In March 2000, an interna-tional evaluation panel, established by theAcademy of Finland, recommendedFinland to join ESO “anticipating furtherincrease in the world-standing ofAstronomy in Finland”. In February 2002,we were invited to hold an informationseminar on ESO in Helsinki as a preludetowards membership. This we did in May2002 and this time six of us went toHelsinki: in addition to Massimo, I wasaccompanied by Ian Corbett, RichardKurz, Claus Madsen and Richard West.The event attracted a great deal of atten-tion and was very successful.

The Finnish Government decided inMarch 2002 to ask for formal negotiations

which started in June 2002, and were con-ducted satisfactorily through 2003, mak-ing possible a visit to Garching on 9February 2004 by the Finnish Minister ofEducation and Science, Ms. TuulaHaatainen, to sign the membership agree-ment together with myself.

Before that, in early November 2003,ESO participated in the Helsinki SpaceExhibition at the Kaapelitehdas CulturalCentre with approx. 24,000 visitors.

ESO warmly welcomes the new mem-ber country and its scientific communitythat is renowned for its expertise in manyfrontline areas. The related opportunitieswill contribute to strengthening of pio-neering research with the powerful facili-ties at ESO's observatories, to the benefitof Astronomy and Astrophysics as well asEuropean science in general. ESO alsolooks forward to collaboration with theFinnish high-tech industry and furtherinteraction in the areas of outreach andeducation.

The Messenger 1172

ESO WESO WELCOMESELCOMES FFINLANDINLAND ASAS EELEVENTHLEVENTH MMEMBEREMBER SSTTAATETE

CCAATHERINETHERINE CCESARSKYESARSKY, , ESO DIRECTOR GENERAL

ESO’s stand at the HelsinkiSpace Exhibition at the

Kaapelitehdas Cultural Centre.

H. H

eyer

(ES

O)

© ESO - September 2004 3

FFINLAND HAS A LONG TRADITION

in Astronomy. The firstUniversity in Finland, theAcademy of Turku (Åbo), wasfounded in 1640, and

Astronomy was taught there from the verybeginning. The first Finnish scientist to riseto world fame was the astronomer and math-ematician Anders Lexell who was appoint-ed Docent of the Academy in 1763. Lexellshowed that a comet, discovered in 1770,would, after a passage close to Jupiter in1779 be slung out of the solar system. Thishappened as predicted, was a great victory ofcelestial mechanics and Newton’s theory,and made Lexell’s name and the cometfamous all over Europe.

In 1748 the first dedicated position inAstronomy, Observator, was established,and in 1817-19 an observatory was built,equipped with the best instruments of itstime. The observator Henrik Johan Walbeckbecame known for his study on the size andshape of the Earth. In 1823, the Academyinvited, following the advice of WilhelmBessel, his pupil Friedrich W. A. Argelanderto the Observator position. Argelander’sgrandfather, a smith and a descendant of thefamily of Kauhanen-Argillander from Savocounty in eastern Finland, had moved toPrussia where his son became a wealthymerchant. Argelander’s activity at the newobservatory was soon to be interrupted bythe great fire of Turku. In his observing log-book of the evening of September 4th, 1827,one can read the following classical state-ment by a scientist living in his “ivorytower”: “These observations were interrupt-ed by a terrible fire which put into ashesalmost the whole city, but thank the Lord, leftthe observatory intact.”

As a consequence of the fire, the capitalof Finland and the University were relocatedto Helsinki. There, a new observatory,designed in close collaboration betweenArgelander and the state architect C. L.Engel, was established in 1834 (Fig. 1). TheObservator position was upgraded to

Professor’s chair in 1828, and Argelanderwas appointed its first holder. Based onaccurate proper motions from his ownmeridian circle observations in Turku andearlier data from others, Argelander pub-lished in 1837 a famous study on the deter-mination of the Solar Apex. However, with-in the same year he moved to Bonn where hefounded a new observatory and rose tobecome one of the leading figures of 19th

century Astronomy. After Argelander, the Observatory par-

ticipated under the leadership of AdalbertKrüger, in the big international catalog workAGK1 of the Astronomische Gesellschaft.At the turn of the century the most extensive

international enterprise in Astronomy so far,the photographic “Carte du Ciel” survey,started with the participation of Helsinki(Anders Donner) and seventeen other lead-ing observatories around the world. Thecelestial mechanics tradition was continuedat the beginning of the 20th century by KarlF. Sundman whose works on the three-bodyproblem brought him international fame.Later on, research in celestial mechanics andrelativity theory was carried out by GustafJärnefelt and Paul Kustaanheimo. Astrophy-sical and Radio Astronomy research wereintroduced at the University of Helsinki byJaakko Tuominen after World War II.

After a hiatus of a hundred years, astron-

Figure 1: Helsinki Observatory, established in 1834, belongs to the group of neoclassi-cal, historical buildings of the centre of the city.

AASTRONOMYSTRONOMY ININ FFINLANDINLAND

AN OVERVIEW IS GIVEN OF ASTRONOMICAL RESEARCH IN FINLAND. THERE ARE THREE INSTITUTES DEVOTED TO

ASTRONOMY IN GENERAL, AT THE UNIVERSITIES OF HELSINKI, OULU, AND TURKU, AND A RADIO ASTRONOMY

OBSERVATORY AT THE HELSINKI UNIVERSITY OF TECHNOLOGY. IN ADDITION, SOLAR SYSTEM RESEARCH WITH

SPACE-BORNE INSTRUMENTATION IS BEING CARRIED OUT BY THE PHYSICS DEPARTMENTS AT THE UNIVERSITIES

OF HELSINKI AND TURKU, AND BY THE FINNISH METEOROLOGICAL INSTITUTE.

KKALEVIALEVI MMAATTILATTILA 11, M, MERJAERJA TTORNIKOSKIORNIKOSKI 22, I, ILKKALKKA TTUOMINENUOMINEN 33, E, ESKOSKO VVALALTTAOJAAOJA 44

1OBSERVATORY, UNIVERSITY OF HELSINKI; 2METSÄHOVI RADIO OBSERVATORY; 3ASTRONOMY DIVISION, UNIVERSITY OF OULU; 4TUORLA OBSERVATORY

omy returned to Turku in 1924 when YrjöVäisälä, the professor of physics at thenewly founded University of Turku, alsostarted giving lectures in Astronomy. Themain interests of Väisälä were classicalastronomy, celestial mechanics, and preci-sion optics. These traditions were continuedby Liisi Oterma and are still active fields inTuorla Observatory, a separate researchinstitute of the University of Turku, whichVäisälä founded in 1951.

Astronomy teaching at the University ofOulu started in the early 1960’s and a profes-sor’s chair was established in 1964 withAntero Hämeen-Anttila as its first holder.His research traditions in celestial mechan-ics and planetary science are being contin-ued by his pupils both in Oulu and Helsinki.

The Metsähovi Radio Observatory,founded in 1975 by Martti Tiuri, then pro-fessor of Radio Technology, is a separateresearch institute of the Helsinki Universityof Technology (HUT). It operates a 14mdiameter radome-enclosed radio telescope(Fig. 2) in Kylmälä, about 35 km west fromthe HUT campus in Espoo.

PPRESENTRESENT RESOURCESRESOURCESThe present personnel resources ofAstronomy in Finland are summarized inTable 1. Besides the four astronomical insti-tutes mentioned above, solar systemresearch is also being carried out by SpacePhysics groups at the Universities ofHelsinki and Turku as well as at the FinnishMeteorological Institute (FMI). Particle cos-mology groups are active at the Universitiesof Helsinki and Turku. In total theAstronomy community in 2003 counted 47senior researchers (including 6 professors inAstronomy and 3 in related fields ofPhysics), 28 Post-docs, 46 PhD students,and 32 technical/administrative staff. Thenumber of PhD degrees awarded was 10.The personnel costs, including salaries andstudent grants, were 5.9 M€, half of whichwas covered by soft money from theResearch Council for Natural Sciences andEngineering, private foundations and similarsources. The running costs were 1.2 M€, theparticipation fees in the Nordic OpticalTelescope (NOT)(29.7% share) andSwedish-ESO Submillimetre Telescope(SEST) (5% share until 30.6.2003) were380 K€. Finland’s membership fee in ESA’sspace science programme was ca. 5 M€,more than half of which can be accountedfor by Astronomy. Two major space instru-mentation projects (Planck 70 GHz receiver;X-ray detector development) received gov-ernment funding, partly via astronomy insti-tutes, in a total of 3.4 M€ in 2003.

Thanks to Finland’s membership of ESAsince 1995 there has been active participa-tion in several of its space missions, includ-ing e.g. SOHO, Cluster, ISO, INTEGRAL,Mars Express. The hardware participation

The Messenger 1174

Figure 2: The 13.7-metre radiotelescope of the MetsähoviRadio Observatory, HelsinkiUniversity of Technology, isenclosed within a 20-metreradome that protects the tele-scope from rain, snow andwind. The surface accuracy ofthe telescope is 0.1 mm (rms).The observing frequencies avail-able at Metsähovi range from 2to 150 GHz, the lower endbeing used for geodetic VLBIand the higher end for millimetreVLBI. The primary observing fre-quencies, however, are in themid-range, 22 and 37 GHz.

Institute Senior staff

Post-docs

PhDstudents

Technical/admin. staff

ObservatoryUniversity of Helsinki

11 5.5 10 7

Tuorla Observatory University of Turku

16 11 13 4

Division of Astronomy University of Oulu

4 7 6 –

Metsähovi Radio Observatory Helsinki University of Technology

4.2 – 1.7 8.4

Dpt of Physical Sciences University of Helsinki and HelsinkiInstitute of Physics

2.6 1.8 8.6 3.3

Dpt of Physical Sciences University of Turku

4 3 4 1

Finnish Meteorological Institute Geophysical Research

5 – 3 8

Table 1. Personnel resources of Astronomy in Finland, year 2003. Included in Astronomy isall space research beyond the Earth’s magnetosphere. (unit: person-years of work).

by institutes and industry in SpaceAstronomy projects since 1995 is listed inTable 2. One ongoing project with particu-larly wide Finnish hardware participation isthe Rosetta Cornerstone Mission (Fig. 3).

In the following chapters we describe inmore detail the current research fields andhighlight some results of the four astronom-ical institutes in Finland.

OOBSERBSERVVAATORTORYY, , UUNIVERSITYNIVERSITY OFOF HHELSINKIELSINKI

Most of the research work at the HelsinkiObservatory is done in three researchgroups: Interstellar medium and star forma-tion; High energy astrophysics; andPlanetary-system research.

Interstellar medium and star formationPhysical and chemical conditions in starforming clouds and the star formationprocess itself are being studied using obser-vations from radio to optical wavelengths,and by applying advanced radiative transfermodelling to their interpretation.

Pre-protostellar and young stellarobjects, still deeply embedded in theirparental molecular clouds, are being detect-ed and physically characterized by using far-IR mappings with the Infrared Space

© ESO - September 2004 5Mattila K. et al., Astronomy in Finland

Program Main partners Finnish participation Launch

SOHO ESA ERNE and SWAN instruments 1995

Huygens ESA HASI instrument, lander radar altimeter 1997

XMM-Newton ESA Telescope structure and satellite electronics 1999

INTEGRAL ESA JEM-X instrument 2002

Mars Express ESA ASPERA-3 instrument, participation in Beagle-2 lander,

satellite power electronics 2003

SMART-1 ESA XSM and SPEDE instruments 2003

Rosetta ESA In Main S/C: OSIMA, ICA, LAP and MIP instruments,satellite power electronics, satellite structure In Philae lander: PP instrument CDMS mass memory

2004

Venus Express ESA ASPERA-4 instrument; S/C power distribution units 2005

Herschel ESA Main mirror 2007

Planck ESA 70 GHz receiver for LFI 2007

Mars-96 RUS Central electronics units, sensors and S/W for landers 1996 failed

Cassini USA Hardware for IBS, CAPS and LEMS instruments 1997

Stardust USA CIDA instrument 1999

Odin SE,CAN,F 119 GHz receiver and antenna measurements 2001

Radioastron RUS 22 GHz VLBI receiver TBD?

Table 2. Finnish space science instrumentation and industrial participation in ESAand bilateral Astronomy missions since 1995.

Figure 3: Rosetta Mission to comet Churyumov-Gerasimenko. The Finnish MeteorologicalInstitute has provided subsystems to four scientific units aboard the main Rosetta spacecraftand is responsible for the permittivity probe and the solid state mass memory of the landerPhilae. Finnish industry has built the mechanical structure of Rosetta and the power distribu-tion system. (Picture ESA)

The Messenger 1176

Figure 5: The left-hand side shows the INTEGRALimage of the field around the micro-quasar GRS

1915+105 (also visible is the new source discoveredduring the observation, IGR J19140+0951). The top-rightdiagram shows an artist’s conception of GRS 1915+105,

which consists of a 14 solar-mass black hole accretingmatter from its companion. In the lower right-hand cor-

ner is the X-ray lightcurve showing the newly discovered5-minute oscillations. (Hannikainen et al. 2003)

Figure 4: a) Clumpy filaments in the Chamaeleon I molecular cloud: the integrated C18O (J=1–0) intensity map measured with SEST. The loca-tions of clumps, identified in the C18O spectral data cube with an automatic routine, are indicated with numbers (Haikala, Harju et al. 2004);b) ISOPHOT 100 µm mapping of the Ced 110 area in Chamaeleon I with four embedded infrared sources indicated as dots (Lehtinen et al. 2001);c) HC3N(J = 10–9) map from SEST of the Ced 110 area with the four embedded sources. The HC3N emission peaks at the position of the Class 0protostar candidate Cha-MMS1 (Kontinen et al. 2000). Recent high resolution ATCA NH3(1,1) mapping by Harju et al. reveals velocity structure,suggesting a proto-binary with precessing jets at this position.

Observatory (ISO) and by molecular linespectroscopy with SEST of nearby molecu-lar clouds (Fig. 4). Interaction between pro-tostellar systems and their immediate sur-rounding ISM have been studied with the aidof high-resolution interferometric radio con-tinuum observations at the AustralianCompact Array ATCA.

The structure, energy balance, and densecore formation in interstellar clouds havebeen studied by applying three-dimensionalradiative transfer codes, which have beendeveloped for both the mm-wave molecularspectral lines and optical-infrared continuumradiation from dust.

Using ISO, the group has also studiedthe properties of the different populations ofinterstellar dust. The distribution and prop-erties of the so-called UnidentifiedInterstellar Bands, probably due to largearomatic molecules like PAHs, have beenstudied over the whole inner Galaxy, and indifferent individual clouds.

The group is studying the ExtragalacticBackground Light (EBL) both at optical andfar infrared wavelengths. Early photometricstudies at La Silla with the “dark cloudmethod” have been described by Mattila andSchnur (1990). Spectroscopic observationsare now going on at the VLT.

The group has been involved as Co-Investigator in the ISO Photometer instru-ment consortium. Several VLT observingprograms have already been carried out.Two previous group members have recentlyserved at ESO positions, one at SEST andanother at the VLT. The group is participat-ing in the relevant Galactic foreground sci-ence projects of ESA’s Planck Mission.

High energy astrophysicsSpecific fields of interest are stellar andsolar coronas and flares, and the mass accre-tion processes in compact binary stars con-taining a white dwarf, a neutron star or ablack hole.

Recent highlights of the group include:• The micro-quasar GRS 1915+105,

consisting of a 14 solar-mass black holeaccreting matter from a red giant, is beingobserved with ESA’s INTErnationalGamma-Ray Astrophysics Laboratory(INTEGRAL). One of the more remarkablefeatures of GRS 1915+105 is the episodicejection of matter at relativistic velocities inbipolar jets. The extreme X-ray variability ofGRS 1915+105 has been categorized into 12distinct classes and INTEGRAL hasrevealed a hitherto undiscovered class char-acterized by 5-minute oscillations seen inthe X-ray lightcurve (Hannikainen et al.2003). Using INTEGRAL, a new source,designated IGR J19140+0951, was discov-ered near GRS 1915+105. Its nature is stillunclear, i.e. whether it is a binary systemcontaining a black hole or a neutron star (seealso Figure 5).

• The puzzling compact binary CygnusX-3 is being constantly monitored usingINTEGRAL and ground based infrared andradio telescopes. Observed properties ofCyg X-3 indicate that the source is closelysimilar to known Galactic black holes CygX-1 and GRS 1915+105.

• Using NOT, the group has opticallymonitored several X-ray emitting binaries.Recently, the candidate for the shortest peri-od binary (RXJ0806+15) has been identi-fied, with an orbital period of only 5 minutes(Ramsay, Hakala, Cropper, 2002). The sys-tem is spinning up, consistent with the pre-dictions of general relativity. Double degen-erate sources like this are expected to be thestrongest constant sources of gravitationalradiation, and are important targets forfuture missions like LISA.

• First results with the XSM X-ray solarmonitor aboard ESA’s SMART-1 missionhave indicated that the XSM 1–20 keV hightime resolution spectra of the full Sun pro-vide a very powerful method for the analysisof individual flare events. Combined withsimultaneous imaging data from other satel-lites, they will also enable semi-empiricalmodelling of X-ray coronas of other stars.

The group also conducts development ofspace science instruments. These includeSMART-1/XSM, SMART-1/D-CIXS, andINTEGRAL/JEM-X. Future plans includeX-ray detectors for ESA’s BepiColombo andXEUS missions, and also new technologysub-mm and infrared detectors. The widerange of technical expertise needed is pro-vided by VTT (Technical Research Centre)and industrial companies (e.g. Metorex,Patria, SSF), which work in close collabora-tion with the Observatory.

Planetary-system researchThe group carries out both physical anddynamical studies of mainly solar-systemobjects. One central area of interest are theasteroids, both their physical properties suchas surface structure, form and rotation, aswell as their orbit determination. Otheratmosphere-less bodies, like the Moon andthe transneptunian objects (TNOs) are alsoincluded.

Theoretical research is focused on scat-tering and absorption of light by single smallparticles and by particulate media. Novelnumerical techniques have been developed,for example, for computation of light scat-tering by non-spherical particles, for model-ling the stochastic Gaussian shapes and clus-ter geometries of small particles, as well asfor coherent backscattering of light by com-plex media of small particles. Laboratoryexperiments are carried out using a scat-terometer device, and the group has signifi-cant responsibilities in the future ICAPS(Interactions in Cosmic and AtmosphericParticle Systems) experiment aboard the

International Space Station. Significantindustrial applications have been found forthe scattering techniques developed.

The research on inverse problemsdivides into the development of mathemati-cal methods and the interpretation of astro-nomical observations. The group has pio-neered in the fields of statistical orbit com-putation for asteroids and asteroid light-curve inversion for their spin vectors andshapes. The group is currently developingstatistical techniques for exoplanet orbitcomputation from radial velocity data aswell as for the asteroid identification prob-lem. The dynamical stability of extra-solarplanetary systems is studied numericallyusing a supercomputing environment.

At NOT, in an effort to accrue in-depthknowledge of near-Earth objects, the groupleads an astrometric and photometricobserving program. At ESO, the group hasstarted an astrometric program at the2.2m/WFI and is participating in polarimet-ric observing programs on TNOs at the VLT.It also makes use of space-borne instrumentsin studies of the Moon (SMART-1) and Mars(Mars Express) and is involved in the prepa-rations of the ESA Cornerstone missionsGaia and BepiColombo.

TTUORLAUORLA OOBSERBSERVVAATORTORYY,,UUNIVERSITYNIVERSITY OFOF TTURKUURKU

Four themes dominate the research: thedynamics of the Universe, from the three-body problem to cosmology; active galaxies,with particular emphasis on high energiesand multi-frequency connections; stars,especially interacting binaries; and finally,ground- and space-based research of ourSun. Väisälä’s tradition of precision opticalengineering is carried on by OpteonCompany at Tuorla. The optical workshop ofTuorla Observatory remains the only placein the world with the capability of polishinglarge silicon carbide mirrors. Work on theHerschel Space Observatory 3.5-metre mir-ror has just begun.

The dynamical universeCosmology is currently in a golden age ofdiscovery. Tuorla researchers are addressingsuch questions as the size and shape of theUniverse, its age, its matter, dark matter anddark energy content, its past and presentexpansion rate and the growth of structureswithin it. Careful mapping of the (cosmolog-ically speaking) local environment, up to afew hundred megaparsecs, can providestrong constraints on cosmology by testingstructure formation via hierarchical collapsein the cold dark matter scenario.

Both dark matter and dark energy canmanifest themselves in various ways onscales of a few Mpc. For example, Tuorlaresearchers are studying the possibility thatthe enigmatic smoothness of the localHubble flow, first recognized by Allan


Sandage over thirty years ago, results fromthe dominance of a perfectly smooth vacu-um density. On still smaller scales, studies ofthe dynamics of our Galaxy have alreadyeliminated black holes and white dwarfs assignificant contributions to the putative darkmatter halo or galactic shroud.

Tuorla researchers are measuring accu-rate distances to our “local sheet” of galax-ies using the tip of the red giant branch, sur-face brightness fluctuations, and planetarynebulae. Beyond these distances, Tuorlaresearchers are building the KLUN+ galaxysample in collaboration with the Paris andLyon groups. On still larger scales, the dis-tribution of clusters and super-clusters isstudied with N-body simulations in a collab-oration with Tartu Observatory. The resultsare compared with the Las Campanas andSloan surveys. Light cone simulations willbe developed for detailed comparisons withfuture observational data. This work is also apart of Tuorla’s involvement in the Plancksatellite project.

On the most fundamental, mathematicallevel, Tuorla researchers have for a longtime been studying the three- to N-bodyproblem and its applications from spacecraftorbits to the dynamics of our Solar System,extra-solar planets, multiple stars and galax-ies. One notable achievement has been theidentification, by York University andTuorla researchers, of the asteroid (3753)Cruithne as a second “moon” of the Earth(Fig. 6).

Active galaxiesRadio and optical monitoring programs ofblazar-type AGN were already started in1980, and continue to provide a uniqueinsight into the long-term behavior of theshocked relativistic jets present in thesesources. During the last decade, the focushas shifted to the highest energies, togamma-rays detected first by the Comptonand now by the INTEGRAL satellite, and toTeV radiation observed with ground-basedCerenkov detectors. Tuorla has joined theinternational MAGIC TeV telescope collab-oration, providing multi-frequency supportin addition to the normal operations. Theother important AGN collaboration is theEU-funded ENIGMA, which organizes largemulti-frequency campaigns. The single dishstudies are supported with extensive VLBAcampaigns.

Most of the work has focused on testingand developing the shocked jet paradigm.Earlier, Tuorla astronomers have found thatall radio variations can be explained bygrowing and decaying shocks in the AGNjets; now the connections to IR and opticalvariations, as well as to the inverse Comptonflux are being investigated using INTE-GRAL and MAGIC data. Evidence has beenfound that the gamma-rays come from theshocks, much farther away from the corethan is usually assumed.

The Messenger 1178

Figure 7: a) The his-torical light curve ofthe blazar OJ 287 for1891-1998. Credit : A.Sillanpää/Takalo andthe OJ Collaboration;b) Model for the binaryblack hole system inOJ 287, the first AGNwith periodic behavior,discovered by Tuorlaresearchers. (Lehtoand Valtonen 1996)

Figure 6: Earth’s second “Moon”: Asteroid (3753)Cruithne has been found by University of York andTuorla researchers to be in a unique heliocentric orbitwhich appears geocentric when viewed from the Earth(Wiegert, Innanen and Mikkola 1997, picture: YorkUniversity)

High resolution imaging with ESO tele-scopes, especially in the near-IR, is beingused to study the cosmological evolution ofAGN, their host galaxies and environments,the relationship between the different class-es of AGN, as well as the star formation his-tory of the hosts. Recent highlights includethe imaging of high redshift host galaxies,the first determination of black hole massesof BL Lac objects, and near-IR spectroscopyof the nuclear regions of Seyfert galaxies.Preparations are also underway for the pre-dicted 2006 outburst of the only known peri-odic AGN, OJ 287, which was identified asa binary black hole by Tuorla researchers in1988 (Fig. 7).

StarsThe stellar research at Tuorla observatoryfocuses on stars with unusual properties:interacting binaries, magnetic cataclysmicvariables (mCvs), intermediate polars, X-raybinaries, white dwarfs, and K dwarfs. Inaddition to seeking answers to many openquestions about the evolution of these stars,these studies also reveal how plasma

behaves in extreme circumstances, such asenvironments with very strong magneticfields. The dwarf stars are essentially stellarfossils, which can be used to study the pro-duction of helium and heavy metals in ourGalaxy.

The group has a unique blend of instru-mental expertise, international collaborationand use of the NOT, multi-wavelength mon-itoring and space observations (ROSAT,XMM). Recent developments include spec-tropolarimetric facilities, and an extensiveobservational program on circular spec-tropolarimetry of mCVs. An ongoing moni-toring campaign of 28 X-ray binaries withthe Nançay radio telescope is the largestever conducted. In the future, the VLT, aswell as the 3.5m class ESO telescopes willenable phase-resolved spectroscopy andspectropolarimetry, including detailed stud-ies of weaker features, such as polarizationin intermediate polars. Ultra-high time reso-lution can also be achieved to map thedetails of accretion discs in eclipsing bina-ries.

The SunThe Tuorla solar group specializes in multi-wavelength analyses of eruptive solarevents. Scientific interests range from parti-cle acceleration to shock waves and plasmaemission, but solar atmospheric models havealso been tested. The long-term use of solarradio data from the Metsähovi radio tele-scope has given the Tuorla group specialexpertise in data acquisition and analysis. Inparticular, Metsähovi observations havebeen used to study the activity in the polarregions of the Sun. Multi-wavelength analy-sis of halo-type coronal mass ejections isbeing carried out in collaboration with theParis Observatory and the Space ResearchLaboratory of the University of Turku, theSOHO ERNE PI institute.

AASTRONOMYSTRONOMY DDIVISIONIVISION, , UUNIVERSITYNIVERSITY OFOF OOULUULU

There are four main research fields in Oulu:stellar and Solar astrophysics; high energyastrophysics; dynamics of planetary ringsand disc galaxies; and planetology of terres-trial planets.


Figure 8: Pole-on views of the primary star ofthe RS CVn binary II Peg for different years.The spots preferably appear near two activelongitudes which migrate over the stellar sur-face. While the total spotted area does not varysignificantly, the relative activity level of thetwo regions changes abruptly in 1994 and1998, indicating “flip-flop” events.

As a highlight of the research carried outin the Astrophysics Group, the project con-centrating on solar-stellar activity is present-ed. It combines powerful observational tech-niques and computational tools. An exten-sive time series has been collected using theSOFIN spectrograph at the Nordic OpticalTelescope. It contains more than ten years ofhigh-resolution spectroscopic observationsof active late-type stars of FK Com- and RSCVn-types, and rapidly rotating solar typestars. The major finding of these investiga-tions has been the persistent two-spot struc-ture in visible hemispheres, two large highlatitude cool areas, spots, situated in oppo-site longitudes (see Fig. 8 and Tuominen,Berdyugina & Korpi 2002). Moreover, theirstrength varies in cyclic manner with a fewyears’ period, the so-called flip-flop effect.In addition to these spectroscopic investiga-tions which use Doppler imaging inversionmethods developed by the group members,the “flip-flop” behavior is also confirmed bylong-term photometric time series.

The recent dynamo models developed inthe group for rapidly rotating stars predictstable non-axisymmetric magnetic fields inthe form of active longitudes. The activelongitudes in the same stellar hemisphere arepredicted to be of opposite polarities. Thereare, however, no definite measurements ofthe magnetic field strength yet and only apreliminary proof of the polarity of the twoactive longitudes for such stars. Also, thereis no information on polarity changes duringstellar cycles. The development of thedynamo models is accompanied by detailedinvestigations on stellar magneto-convec-tion using high-resolution, three-dimension-al turbulence models. Such models haveyielded important revisions of the turbulenttransport quantities needed in the dynamotheory, especially in the rapid rotation limitrelevant for the understanding of the activerapid rotators.

The main research interests of the HighEnergy Astrophysics Group are the process-es in the vicinities of black holes, both stel-lar-mass holes found in X-ray binaries andthe super-massive ones found in the nucleiof Seyfert galaxies, as well as the accretingneutron stars, and the gamma-ray bursts. X-ray and gamma-ray observations are beingcarried out using the Rossi X-ray TimingExplorer (RXTE), INTEGRAL, and othersatellites, and theoretical models are beingdeveloped.

Large efforts are devoted to the analysisof the broad-band X-and gamma-ray spectraof black holes in our Galaxy, such as CygnusX-1 and the micro-quasar GRS 1915+105. Ahybrid thermal/non-thermal Comptonizationspectral model proposed by the group mem-bers was found to describe the observedproperties exceptionally well. In the field ofaccretion-powered X-ray sources, thegroup’s activity is now shifting to the recent-

ly discovered accreting X-ray millisecondpulsars which constitute a link between low-mass X-ray binaries and radio millisecondpulsars. Detailed analysis of the energy-dependent pulse profiles of SAX J1808.4-3658 have provided very strong constraintson the equation of state of the extremelydense matter of neutron stars (Poutanen &Gierliski 2003).

Spectra of the prompt soft gamma-rayemission of gamma-ray bursts are still notexplained and seem mysterious despitestrong theoretical efforts devoted to thisproblem. The Oulu group in collaborationwith the Lebedev Physical Institute inMoscow is now actively involved in a proj-ect to develop the necessary tools to modelthe emission mechanisms. Synchrotron self-Compton emission of nearly mono-energeticelectron-positron pairs seems to explainmost of the observed properties.

The Dynamics Group studies planetaryrings and disc galaxies, combining analyti-cal and N-body modelling with observa-tions. An important result has been the pre-diction of local trailing wake structures inSaturn’s rings (Salo 1992), forming sponta-neously due to mutual gravity between col-liding ring particles. The existence of suchnon-resolved wakes with radial scale of~100 metres is indirectly supported by pho-tometric modelling of global azimuthalbrightness asymmetries seen in Voyager,HST and Arecibo radar data. An intriguingnew prospect is the direct detection of wakesin high resolution Cassini data: like densitywaves driven by external satellite reso-nances, intrinsic wakes provide constraintsfor ring velocity dispersion and viscosity.

The group’s galactic research concen-trates on numerical modelling of prototypi-cal interacting and barred galaxies, and onthe role of bars on the nuclear activity andsecular evolution of disc galaxies. In partic-ular, methods for estimating the bar gravita-tional field from near-IR images are devel-oped and applied to recent galaxy surveys(2MASS, Ohio State University BrightGalaxy Survey). A new observational surveyis also in progress, addressing the barstrength distribution in S0 galaxies as a clueof their origin. Planetary ring studies are per-formed in collaboration with U. Potsdam,Wellesley C. and U. Cornell, and galaxystudies mainly with U. Alabama.

The Planetology Group of the Univer-sity of Oulu studies the surface structures ofterrestrial planets. The strategy of the groupis to combine data from planetary missionsand tools from space science, geosciencesand remote sensing with the group’s ownexpertise in planetology. The goal is to gaina detailed view of the evolutionary process-es which are forming the surface structuresof terrestrial planets.

The group is currently involved in along-term study of Mars. Based on its previ-

ous research experience the group is partici-pating as a Co-Investigator in the HRSC-camera team of ESA’s Mars Express mis-sion. The HRSC data analyses have alreadybegun and will enable, as the data accumu-lates, very detailed investigations of Martiansurface structures.

The group also contributes to the newmission initiatives and participates in otherEuropean space activities within ESA’s plan-etary science program, such as the VenusExpress mission in 2005.

MMETSÄHOVIETSÄHOVI RRADIOADIOOOBSERBSERVVAATORTORYY, H, HELSINKIELSINKI

UUNIVERSITYNIVERSITY OFOF TTECHNOLOGYECHNOLOGYThe main research topics are the multi-fre-quency behavior of active galactic nuclei(AGNs) and the solar microwave radiation.The Metsähovi group is also active in devel-oping radio astronomical instrumentationand measurement methods. Both solar andAGN research is being done in very closecollaboration with the Tuorla Observatory(see also the section on Tuorla Observatoryfor information on the Metsähovi Solarresearch).

Active galactic nucleiThe main research project at Metsähovi isthe study of active galactic nuclei. Dataacross the whole electromagnetic spectrumare being used. However, the backbone ofthe research has always been the long-termmonitoring of the AGN radio variability thathas been going on in Metsähovi since thelate 1970’s. The group has also been veryactive in using the SEST for studying AGNsbetween 1988 and 2003.

The details of the flux density evolutionat various radio frequencies help in model-ling the radio shock formation and develop-ment, and determination of the physicalparameters related to the shock-in-jet struc-ture. Studying the relationships between out-bursts observed in the radio domain andother frequency domains helps to constrainthe models for the high-energy emission inAGNs.

Quick Detection System for the Plancksatellite. The knowledge of the nature, num-ber and behavior of foreground sources isessential for the success of the Planck satel-lite’s primary mission, the measurement ofthe CMB. The group is involved in the studyof the extragalactic foreground sources andis also developing a special software thatwill be used for detecting strong, possiblyflaring, radio sources in the time ordereddata stream of the Planck satellite within 1–2weeks of the time of the observation. Thesupporting theoretical studies in connectionto the software include radio variabilitymodelling of various source types, neededfor defining the triggering criteria for fol-low-up observations.

Inverted-spectrum radio sources. Gigahertz-

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peaked spectrum (GPS) radio sources areextragalactic radio sources characterized byconvex spectra peaking in the GHz rangeand steep at high radio frequencies. Onlyvery few sources with extremely high (> 10GHz) peak frequencies have been reportedearlier. Recently, the group has identifiedseveral new extreme-peaking sources.Identifying high-peaked sources is related tothe work on the Planck satellite’s extragalac-tic foreground.

Work is currently going on with newdata sets from the Metsähovi and RATAN-600 telescopes to search for new high-peaked sources, to study the variabilitybehavior of bona fide GPS sources, to workon the models for inverted-spectrum sourcesand to study the contribution of the high fre-quency tail of the radio spectrum to theextragalactic foreground. Also, VLBI obser-vations have been made of the extreme-peaking sources newly identified by thegroup.

Radio properties of BL LacertaeObjects. The two main BL Lacertae Object(BLO) subclasses, radio-selected BLOs andX-ray-selected BLOs are a product of differ-ent discovery techniques. It is not currentlyknown whether these two classes of objectsare two extremes of one class, or whetherthey have intrinsically different properties.A complete set of BLOs has been observedin Metsähovi, and additional observationsusing other facilities have also been made.

The study of the BLOs is also related to

the Planck foreground science: if some ofthe X-ray selected BLOs turn out to bebrighter than previously assumed, or if thenumber of Intermediate BLOs turns out tobe large, then this information is also essen-tial for the Planck mission.

Correlations between the radio andhigh-energy behavior in AGNs. TheMetsähovi radio monitoring data are alsoused for studying the correlation betweenradio and high-energy domains: activitystates and flares, differences in varioussource populations, etc. Multifrequencyradio-to-submm data and VLBI images areused to study the radio-to-gamma connec-tions. According to the studies of the group,the strong gamma-ray emission in AGNsclearly occurs after the formation of theradio shock in the relativistic jet, i.e. the siteof the gamma-ray emission must be at a dis-tance well outside the accretion disc or eventhe broad line region usually considered tobe responsible for the gamma-ray emission.

InstrumentationAs part of its VLBI instrumentation projectthe group has recently designed and manu-factured next generation VLBI recordingsystems that enable world record data acqui-sition rates: on March 12, 2003, the firstEuropean 1 Gbit/s VLBI experiment and onJune 17, 2003, the first international 2 Gbit/sexperiment.

Along with developing high-speed datarecording systems for VLBI the Metsähovi

team is also developing e-VLBI technolo-gies. The team has been evaluating high-speed Internet protocols for e-VLBI and inthe preliminary data transfer tests, the teamhas achieved an order of magnitudeimprovement to the normal TCP/IP transferspeed.

The Metsähovi group is also involved inthe Alpha Magnetic Spectrometer (AMS)project. This instrument will be placedaboard the International Space Station. Theproject is a very large international collabo-ration project, in which Metsähovi’s respon-sibility is the hardware and software for theground-based high-rate data link, receivingscience data from the instrument.

RREFERENCESEFERENCESHaikala, L., Harju, J., Mattila, K., Toriseva, M.,

2004, A&A, in press (astro-ph/0407608)Hannikainen, D.C. et al., 2003, A&A 411, L415Kontinen, S., Harju, J., Heikkilä, A., Haikala, L.,

2000, A&A 361, 704Lehtinen, K., Haikala, L., Mattila, K., Lemke, D.,

2001, A&A 367, 311Lehto, H. J. & Valtonen, M. J., 1996, ApJ 460, 207Mattila, K., 1990, in IAU Symp. No. 139, The

Galactic and Extragalactic BackgroundRadiation, Eds. S. Bowyer and C. Leinert, p.257

Poutanen, J. & Gierlinski, M., 2003, MNRAS,343, 1301

Ramsay, G., Hakala, P. Cropper, M., 2002,MNRAS, 332, L7

Salo, H. 1992, Nature 359, 619Tuominen I., Berdyugina S. V., Korpi M. J., 2002,

Astron. Nachr., 323, 367Wiegert, P. A., Innanen, K. A., Mikkola, S., 1997,

Nature 387, 685


Is this newly discoveredfeeble point of light thelong-sought bona-fideimage of an exoplanet?

A research paper [1] byan international team ofastronomers [2] providessound arguments infavour, but the definitiveanswer is now awaitingfurther observations.

On several occasionsduring the past years,

astronomical images revealed faint objects, seen near muchbrighter stars. Some of these have been thought to be those oforbiting exoplanets, but after further study, none of them couldstand up to the real test. Some turned out to be faint stellar com-panions, others were entirely unrelated background stars. This onemay well be different.

In April of this year, the team of European and Americanastronomers detected a faint and very red point of light very near(at 0.8 arcsec angular distance) a brown-dwarf object, designated2MASSWJ1207334-393254. Also known as “2M1207”, it is amember of the TW Hydrae stellar association located at a distanceof about 230 light-years. The discovery was made with the adap-

tive-optics supported NACO facility at the 8.2-m VLT Yepun tele-scope at the ESO Paranal Observatory (Chile).The feeble object is more than 100 times fainter than 2M1207 andits near-infrared spectrum was obtained with great efforts in June2004 by NACO, at the technical limit of the powerful facility. Thespectrum shows the signatures of water molecules and confirmsthat the object must be comparatively small and light.

None of the available observations contradict that it may be anexoplanet in orbit around 2M1207. Taking into account the infraredcolours and the spectral data, evolutionary model calculationspoint to a 5 jupiter-mass planet in orbit around 2M1207. Still, theydo not yet allow a clear-cut decision about the real nature of thisintriguing object. Thus, the astronomers refer to it as a “GiantPlanet Candidate Companion (GPCC)”.

Observations will now be made to ascertain whether the motion inthe sky of GPCC is compatible with that of a planet orbiting2M1207. This should become evident within 1-2 years at the most.

ESO Press Release 23/04

[1] The research paper (A Giant Planet Candidate near a Young Brown Dwarf byG. Chauvin et al.) will appear in Astronomy and Astrophysics on September 23,2004 (Vol. 425, Issue 2, page L29). A preprint is available as astro-ph/0409323.

[2] The team consists of Gael Chauvin and Christophe Dumas (ESO-Chile), Anne-Marie Lagrange and Jean-Luc Beuzit (LAOG, Grenoble, France), BenjaminZuckerman and Inseok Song (UCLA, Los Angeles, USA), David Mouillet (LAOMP,Tarbes, France) and Patrick Lowrance (IPAC, Pasadena, USA).

IISS THISTHIS SSPECKPECK OFOF LLIGHTIGHT ANAN EEXOPLANETXOPLANET??

VVISIR stands for VLTImager and Spectrometerfor the mid-InfraRed(mid-IR). This cryogenicinstrument, optimised for

diffraction-limited performance in bothmid-IR atmospheric windows, the N andQ bands (Fig. 1), combines imagingcapabilities with various magnifications,with slit grating spectroscopy with vari-ous spectral resolutions, up to R = 25,000at 10 µm and 12,500 at 20 µm.

The contract to design and buildVISIR was signed in November 1996between ESO and a French-Dutch con-sortium of institutes led by Serviced’Astrophysique of CEA/ DSM/DAP-NIA; the Dutch partner is ASTRON,Dwingeloo. One year after the signatureof the contract, VISIRpassed the PreliminaryDesign Review, whichconcluded that VISIR wasfeasible (Rio et al. 1998).The project passed theFinal Design Review in1999 (Lagage et al. 2000).The instrument was thenmanufactured, integratedand suffered from unex-pected events, such as fireand then flooding in theSaclay building housingthe VISIR laboratory!After extensive tests in thelaboratory (Lagage et al.2003), VISIR was shippedto Paranal in March 2004;after that everything wentvery smoothly. The instru-ment was transported fullyintegrated, so that in April

it could be mounted almost right awayonto Melipal, the third of the four 8.2-mVLT Unit Telescopes (Fig. 2). Firstimages were obtained on May 1st, a fewhours after feeding VISIR with sky light.The second commissioning (from June30 to July 7) was jeopardized by badweather conditions (4 nights fully lostand 3 nights rather poor). During the twocommissioning runs, several observingmodes were sufficiently tested to consid-er to offer them to the community at thenext call for observing proposals (dead-line October 1, 2004). To finish commis-sioning, a third commissioning run tookplace from August 27 to September 5. Allthe VISIR modes have now been suc-cessfully tested. The results from this lastrun will be reported later.

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SSUCCESSFULUCCESSFUL CCOMMISSIONINGOMMISSIONING OFOF

VISIR: VISIR: THETHE MIDMID-- INFRAREDINFRARED VLVLTTIINSTRUMENTNSTRUMENT

VISIR IS THE ESO-VLT INSTRUMENT DEDICATED TO OBSERVATIONS THROUGH THE TWO MID-INFRARED

ATMOSPHERIC WINDOWS (THE SO-CALLED N AND Q BANDS). VISIR WAS INSTALLED IN APRIL 2004 AT THE

CASSEGRAIN FOCUS OF MELIPAL, THE THIRD OF THE FOUR 8.2 METER VLT UNIT TELESCOPES; FIRST LIGHT WAS

OBTAINED ON MAY 1ST. THIS CRYOGENIC INSTRUMENT COMBINES IMAGING CAPABILITIES AT THE DIFFRACTION

LIMIT OF THE TELESCOPE (0.3 ARCSEC AT 10 MICRONS) OVER A FIELD UP TO 51 ARCSEC, AND LONG-SLIT (32ARCSEC) GRATING SPECTROSCOPY CAPABILITIES WITH VARIOUS SPECTRAL RESOLUTIONS UP TO 25,000 AT 10MICRONS AND 12,500 AT 20 MICRONS. THE INSTRUMENT WILL BE OFFERED TO THE COMMUNITY FOR ESOPERIOD 75 (PROPOSAL DUE DATE: OCTOBER 1ST 2004 ).

PP.O. L.O. LAGAGEAGAGE11, J. W, J. W. P. PELEL2,32,3,,M. AM. AUTHIERUTHIER11, J. B, J. BELORGEYELORGEY11,,A. CA. CLARETLARET11, C. D, C. DOUCETOUCET11,,D. DD. DUBREUILUBREUIL11, G. D, G. DURANDURAND11,,E. EE. ELSWIJKLSWIJK33, P, P. G. GIRARDOTIRARDOT11,,H.U. KH.U. KÄUFLÄUFL44, G. K, G. KROESROES33,,M. LM. LORORTHOLARTHOLARYY11,,YY. L. LUSSIGNOLUSSIGNOL11,,M. MM. MARCHESIARCHESI44, E. P, E. PANTINANTIN11,,R. PR. PELETIERELETIER2,32,3, J.-F, J.-F. P. PIRARDIRARD44,,J. PJ. PRAGTRAGT33, Y, Y. R. RIOIO11,,TT. S. SCHOENMAKERCHOENMAKER33,,R. SR. SIEBENMORGENIEBENMORGEN44,,A. SA. SILBERILBER44, A. S, A. SMETTEMETTE44,,M. SM. STERZIKTERZIK44, C. V, C. VEYSSIEREEYSSIERE11

1DSM/DAPNIA, CEA/SACLAY,SACLAY, FRANCE; 2KAPTEYN INSTITUTE, GRONINGEN

UNIVERSITY, GRONINGEN, THE

NETHERLANDS; 3ASTRON (NETHERLANDS

FOUNDATION FOR RESEARCH IN

ASTRONOMY), DWINGELOO, THE

NETHERLANDS; 4EUROPEAN SOUTHERN OBSERVATORY

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Figure 1: Mid-IR transmission of the atmosphere atParanal, computed using the HITRAN model. The Nwindow (8-13 microns) is a good window, especially inthe 11 micron range; the only bad part is around 9.5microns (ozone band). The Q window (17-25 microns)is a poorer window and the transmission depends cru-cially on the water vapour content of the atmosphere.For the transmission given in the figure, good atmos-pheric conditions of 1.5 mm of precipitable watervapour were assumed.

SSCIENTIFICCIENTIFIC CAPCAPABILITIESABILITIESANDAND OBSEROBSERVINGVING MODESMODES

The mid-IR region is the domain of excel-lence to study both warm dust and gas(molecular or atomic) in various objects inthe Universe, from nearby objects such ascomets to quasars. Warm dust at an equilib-rium temperature ranging between 80 and400 K is best detected in the mid-IR throughits thermal emission; grains small enough tobe transiently heated to high temperature,the so-called VSGs (Very Small Grains), canemit in the mid-IR, even if their “mean”temperature is very low. Broad solid-statedust features (for amorphous or crystallinesilicate dust around 10 and 20 microns) areobservable from the ground, as well as theso-called PolyAromatic Hydrocarbonates(PAHs) bands at 12.7, 11.3 and 8.6 microns.Concerning gas transitions, two of the threelowest energy (i.e. pure rotational) quadru-pole transitions of molecular hydrogen in thevibrational ground state (H2(0,0)S(2) at12.28 microns and H2(0,0)S(1) at 17.03microns) are observable from the ground, atleast using high spectral resolution(>10,000) to find them between atmosphericlines. A variety of atomic lines are accessiblefrom ground-based observations in the mid-IR, such as the forbidden lines of [Ne II] at12.8 microns, the [S IV] line at 10.5microns, and [Ar III] at 8.99 microns.

The main advantage when observingfrom the ground in the mid-IR is the highangular resolution achievable with large tel-escopes. Indeed, in this wavelength range,the angular resolution is mainly limited bythe diffraction of the telescope. Until thelaunch of the James Webb Space Telescope(JWST), scheduled for 2011, the angular res-olution achievable using ground-based facil-ities will be 10 times higher than from spacefacilities. With VISIR the diffraction Airypattern of the Spitzer Space Telescope (for-merly known as SIRTF, the Space InfraredTelescope Facility) can be resolved into 100elements (full width half maximum of 2.6arcsec at 10 µm for a 80 cm telescope, to becompared to 0.26 arcsec for a 8-meter classtelescope). Thus, the top priority in theVISIR specifications has been the imagequality.

Of course, the huge atmospheric and tel-escope background dramatically limits thesensitivity achievable with ground-basedmid-IR instruments. Thus the “niche” forground-based mid-IR astronomy is theobservation of relatively bright sources (afew mJy) for which high angular resolutionis needed. Examples of such programs arethe study of circumstellar environments, thestudy of multiplicity in early stages of starformation, …

To conduct the various observing pro-grams with VISIR, several observing modeswere implemented :

• imaging with a choice of 3 magnifica-


Figure 2: Top left: VISIR cable wrap mounted at the Cassegrain focus of MELIPAL. The cablewrap carries the electrical cables and closed-cycle cooler hoses to the instrument and rotateswith it as the telescope tracks objects on the sky. At that time, a mass dummy was mountedon the cable wrap instead of VISIR. Bottom left: the mass dummy has been removed andVISIR, on its carriage, is going to be mounted onto the cable wrap. We can recognize the vac-uum vessel (cylindrical shape with a diameter of 1.2 m and a height of 0.7 m) and the blue cab-inets containing electronics for controlling and monitoring the instrument functions. Just abovethe middle of the blue boxes, we can see one of the three cryocoolers, used to cool the instru-ment to about 20K and the detector arrays to 7K. Right: VISIR fully mounted behind the pri-mary mirror of MELIPAL. The total weight of VISIR is 2.3 tons.

Figure 3: Top left: inside the cryostat; after removing the dome at the back of the cryostat, asshown in Figure 2 (right), one can see two sub-units: the imager (bottom left) and the spec-trometer (top right). Bottom left: inside the spectrometer, partly integrated; one can see the slitwheel, the high-resolution duo-echelle grating (top right) and the grating carrousel carrying the4 gratings including one scanner each for the low- and medium- spectral resolution arm (bot-tom left). Right: VISIR cryostat being assembled; the cryostat consists of a vacuum vessel andradiation screens; the vessel is composed of a flange to interface VISIR with the telescopeadapter rotator (bottom of the image), a cylinder and a dome. The vessel is equipped with aradiation screen with superinsulation to lower the temperature of the surface radiating towardsthe cold optical bench.

tions and 24 narrow- and broad-band filters.The three Pixel Fields Of View (PFOV) are0.075 arcsec, 0.127 arcsec and 0.2 arcsec.The corresponding fields of view are19.2u19.2 arcsec2, 32.5u32.5 arcsec2 and51.2u51.2 arcsec2.

• slit grating spectroscopy with variousspectral resolutions (R=λ/δλ), given for anentrance slit width set to 2λ/D, (where, asusual, λ is the wavelength and D the tele-scope diameter). Three spectral resolutionsare available in the N band: low (R = 350 at10 µm), medium (R = 3200 at 10 µm) andhigh (R = 25,000 at 10 µm). Two spectralresolutions are available in the Q band:medium (R = 1600 at 20 µm) and high (R =12,500 at 20 µm). There is also the possibil-ity to have a low resolution mode in Q band(R = 175 at 10 µm) but the usefulness ofsuch a mode in the poor Q band atmospher-ic window has to be proven. The PFOValong the slit is 0.127 arcsec. There are 28slits with selectable width between 0.3) and4). In low and medium resolution the slitlength is 32 arcsec. The nominal high-reso-lution echelle spectroscopy mode is per-formed with cross-dispersion grisms fororder separation. With these low-dispersiongrisms four to five echelle orders are imagedsimultaneously on the detector. To avoidorder overlap the slit length is reduced to 4.5arcsec for the cross-dispersed mode.Alternatively, for astrophysically importantisolated lines, long slit Echelle spectroscopyobservations are possible. At the momentfour order-selection filters are available toperform long-slit high-resolution echellespectroscopy: H2 at 8.02 microns, [Ne II] at12.81 microns, H2 at 17.03 microns and[S III] at 18.68 microns.

DDESIGNESIGN ANDAND DEVELOPMENTDEVELOPMENTThe choice was made in the early stage ofthe ESO VLT instrumentation plan to haveonly one VLT instrument in the mid-IR, able

to combine imaging and spectroscopy. Thisdecision resulted in VISIR being a rathercomplex multi-mode instrument. On top ofthat, in order to limit the contribution of theoptical bench to the photon background toless than 1%, the optical bench has to becooled to a temperature lower than 60 K forthe imager and lower than 32 K for the spec-trometer. Thus VISIR is a cryogenic instru-ment (Fig. 3).

VISIR is made of two subsystems: animager and a spectrometer. Each subsystemhas its own detector array. The detectors areboth 256u256 Si:As BIB arrays developedby DRS Technologies (Galdemard et al.2003). The acquisition system is the com-mon-user IRACE system developed byESO. The software is based on the generalVLT software. The detectors have to becooled down to ~8K to avoid prohibitivedark current.

The optical design of the imager is anall-reflective system made of five mirrors(Fig. 4). The first mirror images the tele-scope pupil onto a cold stop (18 mm indiameter) to block extra background. Thesecond mirror is a folding flat to ease themechanical implementation. The last threemirrors form a Three Mirror Anastigmat(TMA) configuration. They ensure the re-imaging of the field onto the detector. Thethree magnifications of the imager areimplemented by a set of three TMA systemsmounted on a wheel, named TMA wheel.Near the focal plane another wheel (thediaphragm wheel) is used to adapt theentrance field aperture to the selected mag-nification, in order to limit possible extra-background. Three positions of the wheelare occupied by aperture masks and foldingflats to deflect the telescope beam into thespectrometer. The third wheel of the imageris a filter wheel, which is located just afterthe cold stop and which can hold up to 40filters.

In the spectroscopic mode the telescopebeam enters the spectrometer via the ‘re-imager’ unit with a cold stop, two filterwheels (with order-selection filters and fixedFabry-Perot etalons for wavelength calibra-tion) and an entrance slit wheel (Fig. 4). Theactual spectrometer has two arms, one forLow- and Medium- Resolutions (LMR) andone for the High-Resolution (HR) mode.Like the imager, the spectrometer makes useof Three Mirror Anastigmat systems, butnow in double pass: in the first pass theTMA acts as a collimator, in the second passas a camera. Each arm has its own TMA,with a collimated beam diameter of 125 mmin the HR arm and 53 mm in the LMR arm.Via switchable folding flats the spectra fromboth arms are imaged onto the spectrometerdetector. The LMR arm gives a choicebetween four small reflective gratings. Allare used in 1st order in the Q-band and in 2nd

order in the N-band. The HR arm is builtaround the ‘duo-echelle’: two large echellegratings mounted back-to-back on an alu-minium blank of 350u130 mm. Bothechelles have slightly different rulings (80.0and 77.3 grooves/mm), resulting in two setsof “interlaced” grating orders. By choosingeither the ‘A’ or the ‘B’ side of the duo-echelle, one can select for each wavelengththe grating order with optimum blaze effi-ciency.

Given that VISIR is a cryogenic instru-ment and given the number of modes, theleading mechanical design criteria were high

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Figure 5: Top: Novel compact, precise andcryogenic motor/clutch unit actuator ofVISIR. Such compactness was a key require-ment to achieve a very compact mechanicaldesign, imperative for a cryogenic instru-ment. Bottom: light-weighted structure onthe back of one of the mirrors of the spec-trometer. Also shown are the special mount-ing ‘ears’ for stress-free isostatic mounting.

Figure 4: Optical designs of the VISIRimager (left), and spectrometer (right).

stiffness to weight ratio, low mass and highthermal stability. Such criteria have led tothe development of a novel type of cry-omechanism by the CEA/DAPNIA (Fig. 5).These devices have to actuate, at cryogenictemperature, optical devices with a veryhigh accuracy and positioning repeatability(5 arcsec). By design, the cryomechanismsare very rigid and can be used in a cantileverposition. The concept allows open loop con-trol by use of a stepper motor with hightorque and direct drive and includes a zeroposition switch as well. The power dissipa-tion is zero when the cryomechanism islocked in position. Eleven such cryomech-anisms are used in VISIR: three for theimager and eight for the spectrometer. Thelow mass criterion has also led to light-weighting of the opto-mechanic parts ofVISIR, such as the mirrors (Fig. 5).

PPERFORMANCEERFORMANCEThe image quality of the imager waschecked to be diffraction limited both in Nand Q band (Fig. 6), at least under good see-ing conditions. In the mid-IR at 10 micronsthe influence of atmospheric turbulence onimage quality is obviously much less than atoptical wavelengths. However, it is impor-tant to note that, when the optical seeing isworse than about 0.6 arcsec, a departurefrom diffraction limited performance at 10microns is also observed.

The pupil alignment was also checkedand found to be correct within a few percent(Fig. 7).

The sensitivity depends considerably onthe weather conditions, especially in the Qband. While we achieved reasonable sensi-tivities in the N band (for example, down to3.6 mJy 10σ 1 hour for the 11.3 µm PAH fil-ter in good weather conditions), we were faroff (an order of magnitude) in the Q band.The origin of such bad sensitivity is proba-bly bad weather conditions.

To achieve the required sensitivity, thehuge photon background has to be removed.This is done following the classical chop-

© ESO - September 2004 15Lagage P.O. et al., Successful commissioning of VISIR

Figure 7: N-band pupil image for the spec-trometer. In the thermal infrared, the pupil-image is an inverse of an ‘optical’ pupilimage. What would show up dark in an opti-cal image is radiating strongly at 10 microns.We can see thermal emission of 1) the (circu-lar) M3-tower, 2) the rectangular attachmentof the M3-tower in the stow-position and 3)the spiders of the VLT-M2 with their V-shaped geometry.

Figure 6: Point source with diffraction ringsat 11.2 microns and 19.5 microns.

Figure 8: Illustration of the chopping-nodding technique when observing the He2-10 bluecompact galaxy (see ESO press release about VISIR for more information about the object).The basic idea to remove the huge photon background generated by the atmosphere and thetelescope is to make the difference between two observations: one on-source (backgroundplus source) and the other off-source (background alone). Given the background fluctuationtime scale, the on- and off-source measurements have to be done at a rate typically in the Hzrange. Such a high rate cannot be achieved by moving the telescope. That is why it is done bymoving the secondary mirror of the telescope (positions A and B on the left of the illustration);this is called chopping. The chopping technique allows us to remove the sky background andmost of the telescope background. However the optical path on the primary mirror is notexactly the same according to the chopper position. That is why a residual backgroundremains after chopping and one cannot detect the galaxy (see image labeled nodding A beamin the illustration). The time scale for the fluctuations of the residual background is long andcan be monitored by moving the telescope off source and doing the same chopping observa-tion sequence as in the preceding telescope position (resulting in the image labeled noddingB beam). After subtracting beams A and B, the galaxy is detected. If the chopping throw andnodding throw are small enough, the source is always present in the field of view of the instru-ment, so that we end up with four sources on the final image (two positive and two negative).

ping-nodding technique illustrated in Fig. 8.While the VLT secondary mirror assemblyallows chopping up to typically 5 Hz, sub-stantially lower frequencies are being used,so that active field-stabilisation with theVLT-secondary mirror (M2) while choppingbecomes possible. This is necessary for ulti-mate image quality under typical wind con-ditions. For the commissioning runs chop-ping frequencies as low as 0.25Hz were usedto detect sources at a level of a few tens ofmJy in imaging. Further tests are pending, tosee whether these low frequencies compro-mise the sensitivity.

With VISIR a huge hurdle in improvingground-based mid-IR observation has beenpassed. We knew that with observations on a3-meter class telescope we were only seeingthe “tip of the iceberg” and that improve-ments should be achieved with VISIR. But,we were surprised by what we saw (Fig. 9)!With VISIR, we can obtain from the ground,mid-IR images with a quality rivalling thatof shorter wavelength observations.

The spectrometer is also performingvery well. Complete low-resolution N-bandspectra were taken on July 4 and 6 in foursettings (two with the LSW grating and twowith the LLW grating) for various standardstars. The result for HD 175775 is shown in

Fig. 10. In general the different parts of thespectrum join up quite well. The ratio of thespectra of two standard stars is reasonablyclose to the ideally flat distribution, exceptat wavelengths with strong atmospheric fea-tures like in the ozone band around 9.5microns, where the atmospheric contribu-tions do not cancel sufficiently due to differ-ence in air mass and atmospheric variations.

Of special interest is the high spectralresolution mode, which has, so far, no equiv-alent in the Southern hemisphere (Fig. 11).

OOBSERBSERVINGVING WITHWITH VISIRVISIRVISIR is one of the instruments which willgenerally be used during bright time. Giventhe international competition (for examplethe T-ReCS instrument on Gemini South),VISIR will be offered to the community assoon as possible. The VISIR modes thathave been sufficiently tested during the firsttwo commissionings will be offered to thecommunity in the call for proposals forPeriod 75 (proposal due date: October 1st).

AACKNOWLEDGMENTSCKNOWLEDGMENTSVISIR would have not been possible without thecontributions of numerous people in the consor-tium and at ESO. We would like to thank all thosewho have contributed to this superb instrument:

Staff at Saclay: D. Arranger, A. Bakaou, P.

Bargueden, J.C. Barriere, G. Dhenain, A. Donati,B. Duboue, N. Eyrard, Ph. Galdemard, D. Gibier,J.F. Gournay, E. Gregoire, J.M. Joubert, A.Lotode, P. Magnier, P. Mulet, J. NevesDaCosta, D.Nicolleau, F. Nunio, B. Pinvidic, Y. Sauce, Ph.Seguier, A. Sinanna, J.C. Toussaint, C. Walter.Former Saclay staff, N. Bottu, F. Garnier, E.Guelin, C. Lyraud, G. Wang.

Staff at ASTRON: A. van Ardenne, J. Bakker,M. Bakker, R. van Dalen, S. Damstra, J. Dekker,M. Drost, G. Hagenauw, R. ter Horst, J. Idserda,A. de Jong, T. de Jong, G. Koenderink, Y.Koopmans, A. Koster, J. Kragt, S. Kuindersma, J.Nijboer, P. Pul, M. Schuil, J. Tinbergen, N. Tromp.

Staff at ESO headquarters: E. Allaert, P.Ballester, J.L. Beckers P. Biereichel, B. Delabre,G. Finger, Y. Jung, J.-L. Lizon, L. Lundin, W.Nees, L. Mehrgan, M. Meyer, J. Stegmeier, J.Vinther and former ESO staff: N. Devillard, A.Van Dijsseldonk. The support to the project by G.Monnet and A. Moorwood was crucial, especiallyduring difficult phases.

We wish also to thank the ESO staff onParanal (R. Gilmozzi, J. Spyromilio, A. Kaufer, U.Weilenmann P. Baksai, J. Brancacho, R. Castillo,N. Hurtado, J. Navarrete) for their excellent sup-port during installation and commissioning ofVISIR.

RREFERENCESEFERENCESPh. Galdemard et al. 2003, SPIE Vol. 4841, 129 P.O. Lagage et al. 2000, SPIE Vol. 4008, 1120P.O. Lagage et al. 2003, SPIE Vol. 4841, 923 Y. Rio et al. 1998, SPIE Vol. 3354, 615H. Zinnecker et al. 1996, Messenger 84, 18ESO press release 13/04, May 2004

The Messenger 11716

Figure 11: Left: image in the [NeII] line at 12.8 microns of the “Ant” PlanetaryNebula (Mz3). Right: long-slit high-resolution spectrum around the [NeII] line;spatial direction is horizontal and spectral direction vertical. The slit waslocated as indicated by the line on the left image. The velocity resolution isabout 17km/s.

Figure 10: Full low-resolution N-band spectrum of standard star HD175775(20.2 Jy at 12 µm). Note that the spectra have not been corrected for atmos-pheric effects.

Figure 9: Top : image of thegalactic centre obtained withthe TIMMI instrument mountedon the 3.6-meter telescope onLa Silla (H. Zinnecker et al.1996). Bottom: image of thegalactic centre obtained withVISIR. This illustrates the hugeimprovement when going from a3-meter class to a 8-meter classtelescope.


TThe ESO STC recommended the construction ofSINFONI (“Spectrograph for INtegral FieldObservation in the Near-Infrared”) in October 1997.The instrument was conceived as the combinationof an Adaptive Optics facility (the AO-Module),

developed by ESO, and SPIFFI (SPectrometer for Infrared FaintField Imaging), a Near Infrared Integral Field Spectrograph devel-oped by the MPE. It merges in one instrument the experience gainedby ESO in Adaptive Optics (AO) with the development of theMACAO product line and the experience of MPE in integral fieldspectrometry with 3D, the world’s first infrared integral field spec-trometer.

A two year detailed design phase was initiated in 2000. At thefinal design review (2001), the board recommended the upgrade ofthe instrument to a higher spectral resolution (nearly 4000) with a2048 by 2048 pixel infrared detector. NOVA joined the consortium atthat time to undertake the development of the so-called ‘2K Camera’scaling the spectral images to the size of the new detector.

FFUNCTIONALITIESUNCTIONALITIES

The AO correction is based on the analysis of the wavefront of a ref-erence star picked up close to the science Field of View (FOV). Thesharing of the Cassegrain FOV between the two sub-systems is real-ized by an infrared dichroic mounted at the entrance of the SPIFFIcryostat. The visible flux (450 to 1000 nm) is reflected towards thewavefront sensor and the infrared (1.05 to 2.45 µm) is transmitted tothe science focal plane.

The AO reference star can be acquired up to one arcmin off-axis.

The optimum performance is achieved with stars brighter thanR = 12 mag picked up within ~20 arcsec but fair correction can beobtained in good atmospheric conditions over the full 1u2 arcmin2

FOV with stars up to R = 17 mag. The AO-Module also supports see-ing-limited operations when no guide star is available.

FFIRSTIRST LLIGHTIGHT OFOF SINFONISINFONI AATT THETHE VLVLTTSINFONI IS AN ADAPTIVE OPTICS ASSISTED CRYOGENIC NEAR INFRARED SPECTROGRAPH DEVELOPED BY

ESO AND MPE IN COLLABORATION WITH NOVA. IT WAS SUCCESSFULLY COMMISSIONED BETWEEN JUNE AND

AUGUST AT THE CASSEGRAIN FOCUS OF VLT UT4 (YEPUN). THE INSTRUMENT WILL BE OFFERED TO THE COM-MUNITY FROM APRIL 2005 ONWARDS (PERIOD 75) AND WILL PROVIDE A UNIQUE FACILITY IN THE FIELD OF HIGH

SPATIAL AND SPECTRAL RESOLUTION STUDIES OF COMPACT OBJECTS (STAR-FORMING REGIONS, NUCLEI OF

GALAXIES, COSMOLOGICALLY DISTANT GALAXIES, GALACTIC CENTRE ETC.).

HHENRIENRI BBONNETONNET 11, R, ROBEROBERTOTO AABUTERBUTER 22, A, ANDREWNDREW BBAKERAKER 22, W, WALALTERTER BBORNEMANNORNEMANN 22, A, ANTHONYNTHONY

BBROWNROWN 88, R, ROBEROBERTOTO CCASTILLOASTILLO 11, R, RALFALF CCONZELMANNONZELMANN 11, R, ROMUALDOMUALD DDAMSTERAMSTER 11, R, RICHARDICHARD DDAAVIESVIES 22,,BBERNARDERNARD DDELABREELABRE 11, R, ROBOB DDONALDSONONALDSON 11, C, CHRISTOPHEHRISTOPHE DDUMASUMAS 11, F, FRANKRANK EEISENHAUERISENHAUER 22, E, EDDIEDDIE

EELSWIJKLSWIJK 99, E, ENRICONRICO FFEDRIGOEDRIGO 11, G, GERERTT FFINGERINGER 11, H, HANSANS GGEMPERLEINEMPERLEIN 22, R, REINHARDEINHARD GGENZELENZEL 2,32,3,,AANDREANDREA GGILBERILBERTT 22, G, GORDONORDON GGILLETILLET 11, A, ARMINRMIN GGOLDBRUNNEROLDBRUNNER 22, M, MAATTHEWTTHEW HHORROBINORROBIN 22, R, RIKIK TERTER

HHORSTORST 99, S, STEFTEFANAN HHUBERUBER 22, N, NORBERORBERTT HHUBINUBIN 11, C, CHRISTOFHRISTOF IISERLOHESERLOHE 2,42,4, A, ANDREASNDREAS KKAUFERAUFER 11,,MMARKUSARKUS KKISSLERISSLER-P-PAATIGTIG 11, J, JANAN KKRAGTRAGT 99, G, GABBYABBY KKROESROES 99, M, MAATTHEWTTHEW LLEHNEREHNERTT 22, W, WERNERERNER LLIEBIEB 22,,

JJOCHENOCHEN LLISKEISKE 11, J, JEANEAN-L-LOUISOUIS LLIZONIZON 11, D, DIETERIETER LLUTZUTZ 22, A, ANDREANDREA MMODIGLIANIODIGLIANI 11, G, GUYUY MMONNETONNET 11,,NNICOLEICOLE NNESVESVADBAADBA 22, J, JONAONA PPAATIGTIG 11, J, JOHANOHAN PPRAGTRAGT 99, J, JUHAUHA RREUNANENEUNANEN 11, C, CLAUDIALAUDIA RRÖHRLEÖHRLE 22, S, SILILVIOVIO

RROSSIOSSI 11, R, RICCARDOICCARDO SSCHMUTZERCHMUTZER 11, T, TONON SSCHOENMAKERCHOENMAKER 99, J, JÜRGENÜRGEN SSCHREIBERCHREIBER 2,52,5, S, STEFTEFANAN

SSTRÖBELETRÖBELE 11, T, THOMASHOMAS SSZEIFERZEIFERTT 11, L, L INDAINDA TTACCONIACCONI 22, M, MAATTHIASTTHIAS TTECZAECZA 2,62,6, N, NIRANJANIRANJAN TTHAHATTETTE 2,62,6,,SSEBASTIENEBASTIEN TTORDOORDO 11, P, PAULAUL VVANAN DERDER WWERFERF 88, H, HARALDARALD WWEISZEISZ 77

1EUROPEAN SOUTHERN OBSERVATORY; 2MAX-PLANCK-INSTITUT FÜR EXTRATERRESTRISCHE PHYSIK, GARCHING, GERMANY;3DEPARTMENT OF PHYSICS, UC BERKELEY, USA; 4UNIVERSITÄT KÖLN, GERMANY; 5MAX-PLANCK-INSTITUT FÜR ASTRONOMIE,

HEIDELBERG, GERMANY; 6OXFORD UNIVERSITY, UK; 7INGENIEURBÜRO WEISZ, MÜNCHEN, GERMANY; 8LEIDEN OBSERVATORY,NOVA, THE NETHERLANDS; 9NETHERLANDS FOUNDATION FOR RESEARCH IN ASTRONOMY

Figure 1: Principle of SPIFFI.

SPIFFI obtains spectra for each spatialelement of its two-dimensional FOV. Itsfunctional principle is shown in Fig. 1. Aftersome processing of the raw data the outcomeis a data cube, with 2 spatial (64 by 32 pix-els) and one spectral (2048 pixels) dimen-sions. Spatially, three magnifications areoffered. The high-resolution mode, with 25masu 12.5 (milli-arcsec) per pixel, providesa Nyquist sampling of the diffraction-limitedPoint Spread Function (PSF) at 2 µm with anarrow FOV (0.8u0.8 arcsec2). This modewill offer spatially resolved spectral data oncosmologically distant galaxies, but will belimited by readout noise in many applica-tions even in the case of long integrations(30 minutes). The intermediate pixel scale(100 u 50 mas/pixel) offers the best com-promise between FOV, sensitivity and spa-tial resolution for most applications. Thecoarse mode (250 u 125 mas/pixel) is suit-able for seeing-limited operations and also,thanks to its “wide” 8u8 arcsec2 FOV, isvery useful to help identifying the target dur-ing the acquisition.

Four spectroscopic modes are support-ed: the J-, H- and K-band gratings provide aspectral resolution of approx. 2000–4000. Alower resolution (~2000) is achieved withthe combined H and K grating.

IINSTNSTALLAALLATIONTION ANDAND

COMMISSIONINGCOMMISSIONING SEQUENCESEQUENCE

The integration of SPIFFI with the “1KCamera” was completed at the beginning of2002 in a configuration enabling a directinterface to the VLT for seeing-limitedobservations. SPIFFI was then operated as aguest instrument without AO for a period ofthree months, producing outstanding scien-tific data (see The Messenger 113, 17) aswell as valuable experience in preparationfor the AO-assisted operations. The instru-

ment was then shipped back to Europe andconditioned to interface to the AO-Module.The integration of the latter and its perform-ance demonstration in the laboratory werecompleted in December 2003. The two sub-systems were coupled for the first time in theESO Garching integration facility in January2004 and the Preliminary Acceptance inEurope was awarded in March. The 2KCamera and Detector assembly was thenintegrated in SPIFFI while the AO-Modulewas shipped to Chile for re-integration andstand-alone commissioning on the sky.

The first “AO” light was obtained onMay 31st. On this occasion, an Infrared TestCamera was mounted at the AO-Modulecorrected focus to provide direct imagingcapabilities (Fig. 2). The adaptive opticsloop was immediately closed on a bright star(mV ~ 11) and provided a corrected imageconcentrating into a diffraction-limited core56% of the energy in the K-band (λ = 2.2µm,Figure 3). This performance conformed toexpectations based on laboratory experi-

ments and the experience obtained with thetwo MACAO systems that had already beentested at the Coudé foci of the VLTs.

The re-integration of SPIFFI with theAO-Module took place in the assembly hallof Paranal in June and SINFONI first lightwas obtained on July 9 (Fig. 4). The firstcommissioning was devoted to the testing ofall the observing modes and the tuning of themany automatic control loops which willultimately make this complex instrumentuser-friendly. The success of the July runallowed for dividing the August commis-sioning run among commissioning activitiesfor fine-tuning operations, ScienceVerification and Guaranteed TimeObservations.

OOPENINGPENING TOTO THETHE COMMUNITYCOMMUNITY

The instrument is currently equipped with anengineering-grade detector that is suitablefor technical qualification but affected byflaws which would limit the science capabil-ities of SINFONI. The final science-gradedetector is currently undergoing characteri-zation tests in Garching and will be integrat-ed in the instrument in November.

Meanwhile, the first call for proposals tothe astronomical community will be issuedin September and the start of regular obser-vations is scheduled for Period 75 (startingApril 1st 2005).

Adaptive Optics correction requires thepresence of a reasonably bright referencestar in the vicinity of the science target. Thisconstraint limits AO operations to a smallfraction of the sky. This limitation will beovercome as soon as Yepun (UT4) isequipped in 2005 with a Laser Guide StarFacility (LGSF). The LGSF will launch a10W Sodium laser beam along the telescopeline of sight to create an artificial beacon inthe high atmospheric sodium layer(~100km), providing a reference for wave-front sensing. The upgrade of SINFONI tolaser guide star operations is foreseen for thesecond quarter of 2005.

The Messenger 11718

Figure 2: TheAO-Module atthe VLT UT4Cassegrainfocus for itsstand-alonecommission-ing. The AOoptical benchis the light-blue ring. Itinterfaces tothe VLTCassegrainflangethrough theAO-Housing(intermediatering) and theinterfaceflange (topdark ring).The yellowtest structuresimulates the mass of SPIFFI and provides the mechanical interface to the Infrared TestCamera (aluminum box in the yellow ring).

Figure 3: AO-Module firstlight. The magnitude of thestar is ~11 in V, the seeing0.65 arcsec. The measuredStrehl is 56% (λ = 2.16 µm).The displayed FOV is 0.5arcsec, with a sampling of15 mas/pixel.

IINSTRUMENTNSTRUMENT OOVERVERVIEWVIEWTTHEHE AADAPTIVEDAPTIVE OOPTICSPTICS MMODULEODULE

Optical layoutThe AO-Module was developed in the ESOheadquarter laboratory in Garching (Bonnetet al. 2003). It consists in an optical relayfrom the VLT Cassegrain focus to theSPIFFI entrance focal plane, which includesa deformable mirror conjugated to the tele-scope pupil. The curvatures of the 60 actua-tors are updated at 420 Hz to compensate forthe aberrations produced by the turbulentatmosphere. The optical layout is shown inFig. 5.

At the reflected focus, a pick-up lensmounted to a tri-axial linear stage collectsthe visible flux of the AO guide star, whichis then imaged on the membrane mirror. Thewavefront sensor box (mirrors M1 to M4)collimates the beam and re-images the pupil(conjugated to the deformable mirror) on thelenslet array. There, the flux is split among60 sub-apertures and forwarded to a secondarray of lenslets, which image the sub-aper-tures on the cores of 60 optical fibers. Thephotons are then guided to 60 AvalanchePhoto Diodes (APDs) located in a cabinetmounted to the instrument housing.

In closed loop, a speaker located at theexit of an acoustic cavity forces the mem-brane mirror to oscillate at 2.1kHz. As aresult, the pupil plane moves back and forthalong the optical axis allowing the lensletarray to intercept alternatively the intra- andextra-focal regions. An aberration in thewavefront would de-collimate the beam

locally, causing the flux density to varyalong the optical axis. As APDs are read outsynchronously with the oscillations, the rel-ative intensity difference between the intra-and extra-focal phases is proportional to thelocal wavefront curvature. This signal isused to generate the corrective command tothe deformable mirror. The correction isupdated at 420Hz, with a closed-loop band-width of 30 to 60Hz. The control gains areoptimized for the actual atmospheric condi-tions and the guide-star brightness.

Additional opto-mechanical elementsare already integrated in the AO-Module inview of the Laser Guide Star mode opera-tions. They are not shown in the optical lay-out of Fig. 5.

Performance demonstration on the skyThe Infrared Test Camera (ITC) mounted tothe AO-Module during the stand-alone com-missioning run of June was used to demon-strate the performance of the AO-Module.The ITC provides direct imaging over a fair-ly large FOV (15u15 arcsec2) with a sam-pling adapted to the diffraction-limited PSFin the near infrared (15 mas/pixel).

The typical AO-corrected PSF of a starfeatures a diffraction-limited core superim-posed on a larger halo generated by uncor-rected high-order aberrations. The quality ofthe correction is evaluated with the Strehlratio, computed as the fraction of the incom-ing energy which falls into the diffraction-limited core. In addition to the star bright-ness, the Strehl ratio is driven by the ampli-tude and the coherence time (τ0) of the see-ing: in poor seeing conditions, the PSF isblurred by the larger amplitude of the high-order aberrations, while the AO-Modulereactivity becomes insufficient for fast see-ing conditions.

The measured performance of the AO-

© ESO - September 2004 19Bonnet H. et al., First Light of SINFONI

Figure 4: SINFONIduring installation atUT4. The SPIFFI cryo-stat vessel is the greyaluminum part belowthe AO-Module (blue).To the left, the M1 cellof the VLT.

Figure 5: Optical layout of the AO-Module.

Figure 6: Strehlmeasurements

obtained during AO-Module commission-

ing. Red squaresshow the specified

Strehl performance.Black (resp. blue) dots

are values obtainedwith τ0 > 3 ms (resp.

τ0 < 3 ms )

Str

ehl r

atio

Module is plotted vs. the guide-star magni-tude in Fig. 6. Black dots are Strehl ratiosobtained in conditions better than the medi-an Paranal atmosphere, i.e. with a seeing< 0.65) in the visible and a τ0 > 3 ms, forwhich the AO-Module was specified (speci-fications are shown by the red squares).Strehl ratios obtained in degraded conditionsare plotted in blue, for which the reductionin performance is larger than expected fromthe experience of the other MACAO sys-tems. We believe that they were caused by aloss of bandwidth of the instrument inducedby a variation of the membrane mirror gain

between the laboratory and the telescopeenvironmental conditions.

An illustration of the image qualityachieved in good conditions with a brightreference star is given in Figure 7, whichdisplays a pair of stars with similar magni-tudes (~7.5) and a separation of 0.75). Thebrightest component was used as the refer-ence star, with an absorbing filter dimmingthe flux by 2.5 magnitudes to avoid saturat-ing the detectors of the wavefront analyzer.The Strehl ratio cannot be estimated due tothe saturated peak of the bright component,but the image quality can be qualitatively

appreciated from the number of visible Airyrings.

The ability to perform AO correctionson faint guide objects is essential forSINFONI in order to enable observations offaint extragalactic objects without nearbybright reference stars. This capability wasdemonstrated for good seeing conditionswith a star of magnitude 17.5 (see Figure 8).The measured Full Width at Half Maximum(FWHM) of the corrected PSF in K-bandwas 0.145) while the uncorrected FWHMwas 0.38).

Figure 9 shows the reconstructed 3.6-day orbit of Linus, a satellite of Kalliope.Kalliope is a 180km-diameter asteroid orbit-ing the sun from within the asteroid mainbelt, between the orbits of Mars and Jupiter,at nearly three times the Earth-Sun distance(three astronomical units). The binary sys-tem was observed in early June 2004 overfour consecutive nights using the SINFONIAO module. Due to the geometry of thebinary system at the time of the observa-tions, the orbital plane of the satellite wasseen at an angle of 60 degrees with respectto our line of sight. In fact, the satellite(~50km diameter) revolves around Kalliopeon a 2000km-diameter circular orbit, with adirection of motion similar to the rotationspin of Kalliope (prograde rotation). Thediscovery of this asteroid satellite, namedLinus after the son of Kalliope, the Greekmuse of heroic poetry, was reported inSeptember 2001 by a group of astronomersusing the Canadian-France-Hawaii tele-scope in Hawaii (IAUC 7703). Additionalobservations of Kalliope have been obtainedsince 2001, which led to the determinationof the main orbital characteristics of thisbinary system. Although Kalliope was previ-ously thought to consist of metal-rich mate-rial, the discovery of Linus allowed scien-tists to derive a low ~2 g/cm3 mean densityfor Kalliope. This number is inconsistentwith a metal-rich object and Kalliope is nowbelieved to be a rubble-pile stony asteroid.Its porous interior is due to a catastrophiccollision with another smaller asteroidwhich occurred early in its history and gavebirth to Linus. The VLT data obtained withthe AO-Module of SINFONI will help refineour knowledge of the orbital characteristicsand structural properties of this binary sys-tem.

Finally, the most impressive image sofar was obtained during the August commis-sioning with SPIFFI: the Einstein Cross(Figure 10), a quadruple image of a singleQSO amplified by the gravitational lensinginduced by the foreground galaxy visible atthe centre of the cross. This H-band recon-structed image was obtained with 20 min-utes of integration time in the intermediateplate scale. The AO-Module was guiding onthe brighter southern component, with avisual magnitude of 16. The total extension

The Messenger 11720

Figure 7: Observation of a binary system with a separation of 0.75). To the left, open loopimage acquired with a seeing of 0.6 arcsec. To the right, closed loop image obtained in thesame conditions. The brighter component (lower right) served as a reference for the wave-front sensing. The additional “companions” at the lower left of the PSF cores are ghostimages produced by a multiple reflection at the entrance window of the Infrared TestCamera.

Figure 8: Performance ofAO-Module on faint

guide star (visual magni-tude 17.5). To the right,

the seeing-limited K-band image (FWHM 0.38

arcsec). To the left, theAO-corrected image

(FWHM 0.145 arcsec).The ability to perform AOcorrections on very faint

guide objects is essentialfor SINFONI observations

of faint extragalacticobjects.

Figure 9: Image of asteroidKalliope and its satelliteLinus. The frames wereacquired over four consecu-tive nights, surveying acomplete orbital revolutionof the system. The bright-ness of the central body(Kalliope) has been scaleddown by a factor 15 toreduce the contrast withLinus. Changes in the sizeof the unresolved Linusimage are due to variableseeing conditions from nightto night.

of the system is 1.8 arcsec, making it a verychallenging target for the wavefront sensordue to its complex structure and low bright-ness. The seeing conditions were excellentduring this integration (~0.5 arcsec with τ0 ~4ms).

TTHEHE NEARNEAR-- INFRAREDINFRARED INTEGRALINTEGRAL FIELDFIELD

SPECTROMETERSPECTROMETER SPIFFISPIFFISPIFFI was developed at the MPE(Eisenhauer et al. 2003) in collaborationwith NOVA and ESO. It provides imagingspectroscopy of a contiguous, two-dimen-sional field of 64 u 32 spatial pixels in thewavelength range from 1.1 – 2.45 µm at aresolving power of 2000 to 4000. As a result,the instrument delivers a simultaneous,three-dimensional data-cube with two spa-tial dimensions and one spectral dimension.Originally equipped with a 10242 pixeldetector, SPIFFI was upgraded with a newcamera unit built by NOVA and a HAWAII20482 RG detector array from Rockwell inthe two months between the SINFONI sys-tem tests in Garching and the commission-ing in Paranal. The integral field unit ofSPIFFI is a so-called mirror slicer (Tecza etal. 2002). This image slicer consists of twostacks of 32 plane mirrors, cutting the fieldof view into 32 narrow stripes and rearrang-ing these slitlets to form a single long slit.Depending on the selected image scale, theFOV of the integral field unit ranges from8) u 8) for seeing-limited observations to0.8) u 0.8) for imaging spectroscopy at thediffraction limit of the VLT. The intermedi-ate magnification with a 3.2) u 3.2) field ofview provides a compromise betweenreduced spatial resolution and improved sen-sitivity, and is best-suited for AO-assistedobservations of objects with low surfacebrightness. The slit width in the three imagescales is 250, 100, and 25 mas, with equiva-lent pixel sizes of 125, 50, and 12.5 mas.SPIFFI is equipped with four directly ruledgratings optimized for covering the atmos-pheric J, H, K, and combined H+K bands ina single exposure. The spectral resolvingpower for the 250 mas slit width is about

2000 in J, 3000 in H, 4000 in K, and 2000 inH+K. When using the adaptive optics imagescale, the spectral resolving power increasesup to about 2400 in J, 5500 in H, 5900 in K,and 2700 in H+K, but spectral dithering isnecessary to recover the full resolution fromthe undersampled spectra. The entire instru-ment is cooled with liquid nitrogen to a tem-

perature of –195° C. Figure 11 shows aninside view of SPIFFI.

A quick-look image reconstructionallows the instantaneous display of thereconstructed image during acquisition andobserving. SPIFFI is equipped with its owndata-reduction software, which is presentlyimplemented in the VLT data-reduction


Figure 10: Reconstructed H-band image of theEinstein cross obtained with SINFONI using the100mas/pix mode (image size 3)x3)) under very

good seeing conditions (0.45)). This image demon-strates the capability of the MACAO AO system to

sharpen the images of faint astronomical objects(here the guide star is the brighter component andhas V=16 mag). The Einstein cross was discoveredin 1985 and is one of the best-known examples of

gravitational lensing. A massive black hole at thecentre of a nearby galaxy, located along the line ofsight to a distant quasar, deforms the geometry of

space in its immediate surroundings. As a result,the light from the quasar reaches us through differ-ent paths as if the quasar was observed through a

kaleidoscope, creating multiple images of the sameobject. This special optics distorts and magnifies

the light of background quasars, providing a meansof probing the distribution of intervening matter in

the cosmos.

Figure 11: An inside view of SPIFFI: the cryostat cover and the reinforcing structure havebeen removed to provide a view of the opto-mechanical components of SPIFFI. The lightenters from the top. The pre-optics with a filter-wheel and interchangeable lenses pro-vides three different image scales. The image slicer rearranges the two-dimensional fieldinto a pseudo-long slit, which is perpendicular to the base plate. Three diamond-turnedmirrors collimate the light on the gratings. In total, four gratings are installed on the grat-ing drive. A multiple-lens system then focuses the spectra on a Rockwell HAWAII array.In the meantime the spectrometer has been upgraded with an 20482 pixel detector anda new spectrometer camera. The diameter of the instrument vessel is 1.3 m.

pipeline. This software package provides alltools for the calibration and reduction ofSPIFFI data, including wavelength calibra-tion and image reconstruction. The final dataformat is a three-dimensional data cube with64 u 60 spatial pixels, and up to ~4500spectral elements.

Table 1 lists the limiting magnitudes forthe observation of a point source in the vari-ous instrument configurations.

FFIRSTIRST SCIENCESCIENCEFROMFROM COMMISSIONINGCOMMISSIONING

In addition to performance characterizationand optimization, the commissioning runswere used to explore the capabilities of theinstrument via test observations on a selec-tion of exciting astronomical targets.

DDIFFRACTIONIFFRACTION--LIMITEDLIMITED INTEGRALINTEGRAL--FIELDFIELD SPECTROSCOPYSPECTROSCOPY OFOF THETHE

GGALACTICALACTIC CCENTREENTRE

Because of its proximity of only 8 kpc, thecentre of the Milky Way is a unique labora-tory for studying physical processes that arethought to occur generally in galactic nuclei.The central parsec of our Galaxy contains adense star cluster with a remarkable numberof luminous and young, massive stars, aswell as several components of neutral, ion-ized and extremely hot gas. For two decades,evidence has been mounting that theGalactic Centre harbors a concentration ofdark mass associated with the compact radiosource SgrA* (diameter about 10 light min-utes), located at the centre of that cluster.Measurements of stellar velocities and (par-tial) orbits with the ESO NTT (SHARP) andVLT (NACO) have established a compellingcase that this dark mass concentration is amassive black hole of about 3.5⋅106 M0

(Schödel et al. 2002). The Galactic Centrethus presently constitutes the best proof wehave for the existence of massive blackholes in galactic nuclei. High-resolutionobservations offer the unique opportunities

to stringently test theblack-hole paradigm andstudy stars and gas in theimmediate vicinity of ablack hole, at a level ofdetail that will never beaccessible in any othergalactic nucleus. AO-assisted integral-fieldspectroscopy will play aunique role in studyingthis important region.

The Galactic Centrewas observed duringSINFONI commission-ing on July 15, 2004, forabout 2 hours in ~0.6)seeing conditions. TheAO-Module was lockedon a 14.6 mag star locat-

ed about 20) to the north-east of SgrA* andthe centre of the star cluster. We observedwith the finest plate scale (0.0125) u 0.025)per pixel) and the H+K grating (resolvingpower ~2000). Figure 12 (left insets) showsthe K cube collapsed into a quasi-continuumimage whose FWHM resolution is 75 mas,i.e. very close to the diffraction limit of theVLT in the K band. The Strehl ratio wasabout 10% in K band but is wavelengthdependent.

The SINFONI data provide for the firsttime a complete census of the near-IR spec-tra of most K ≤ 16 stars within about 20light-days of the black hole. The right upperinsets of Figure1 show that a number ofthese “S-stars” exhibit HI Brγ (and HeI)absorption, characteristic of early type, O–Bmain sequence stars. In fact we find that atleast 2/3 of all stars with K ≤ 16 in the cen-tral arcsecond have Brγ in absorption. Thisfinding increases dramatically the ‘paradoxof youth’ (Ghez et al. 2003), as to how these

massive and presumably young stars havemanaged to reside in the central few tens oflight days around the black hole. A numberof ideas have been put forward, including insitu formation in an extremely dense circum-nuclear gas disc, in-spiraling of a massiveyoung star cluster, perhaps aided by interme-diate-mass black holes, scattering by stellarblack holes, and collisional build-up of mas-sive stars from lower-mass stars, but none isso far fully convincing. The orbital proper-ties of the S-stars, now better constrainedwith the radial velocities obtained bySINFONI, promise to give important addi-tional clues to the origin of the massive cen-tral star cluster.

Additional SINFONI observations onJuly 16 also provide new information on thespectral properties of massive blue super-giants further away from SgrA*. An AO-assisted observation of IRS13 E (lower rightinset in Fig. 12), for the first time permittedspatially resolved spectroscopy of all threemajor components of this compact concen-tration of stars, which has been proposed tobe the remnant core of an in-spiraling youngstar cluster. We find that all these three com-ponents have the characteristics of differenttypes of Wolf-Rayet stars.

During the observations of July15 wehad the good luck to catch a small flare ofinfrared radiation from SgrA* itself (lowerleft inset in Fig. 12). These infrared flares,seen for the first time in NACO observationslast year (Genzel et al. 2003 b), probablysample in-falling hot gas in the immediatevicinity of the event horizon. By revealingthe spectral properties of this flare theSINFONI data offer key new insights intothe emission processes that cause infraredflares.

These few hours of data taken on theGalactic Centre during commissioning pro-

The Messenger 11722

Slit width 250 mas 100 mas 25 mas

J Band 18.0 18.5 17.0

H Band 17.5 18.5 17.3

K Band 16.9 18.0 17.2

H+K Band 17.7 18.9 18.2

Table 1: Limiting magnitudes for the observations of a pointsource. The sensitivities are calculated for a signal/noise of 10per spectral channel and one hour integration on source (6 x 10minutes, plus additional sky observations). We assume that50%, 50%, and 25% of the flux is encircled within a diameter of0.65), 0.2), and 0.1) for seeing-limited observations with the 250mas slitlets, and AO assisted observations with the 100 mas and25 mas slitlets, respectively.

Figure 12:Diffraction-limit-ed integral-fieldspectroscopy of

the GalacticCentre with

SINFONI. Thebackground

image shows acomposite

H,Ks,L’-band,three-colour

image taken withthe AO imager

NACO, delineat-ing the distribu-

tion of the differ-ent types of

stars and the hotinterstellar dust

in the centralparsec.

vide a small glimpse of the fantastic infor-mation that diffraction-limited spectroscopywill bring for Galactic Centre (and star clus-ter) research in the next few years. More willundoubtedly follow next year when theinstrument becomes available for scienceexploitation.

A A SHARPSHARP LOOKLOOK AATT

ACTIVEACTIVE GALACTICGALACTIC NUCLEINUCLEI

The role of star formation in active galacticnuclei (AGN) has long been a contentiousissue. Increasing evidence that starbursts dooccur in the vicinity of at least some AGNhas led to a change in thinking from the“starburst or black hole” debate of the last10–20 years to a new framework in whichthe fundamental questions concern thephysics linking the two phenomena. This ismore than just an issue of driving gas in tosmall scales because AGN and star forma-tion activity impact each other via feedbackmechanisms. But the extent of this interac-tion can only be ascertained by addressinghow common, how extended, how recent,and how energetically significant starburstsaround AGN are. Commissioning observa-tions of the Circinus galaxy and NGC 7469

demonstrate the potential of SINFONI toprobe the environment around AGN onsmall scales, and to reveal in detail the dis-tribution and dynamics of both the stellarand gaseous components.

The Circinus galaxy harbours a Seyfert2 nucleus and, at a distance of only 4 Mpc,is one of the nearest such objects. Althoughthe AGN itself is highly obscured, the com-pact K-band core also reveals the AGN indi-rectly, since it has a non-stellar origin: thedistribution of the stellar continuum isrevealed by the CO 2–0 absorption band-head at 2.29 µm to have a much broader dis-tribution. This more extended morphology isalso reflected in the H2 1–0 S(1) 2.12µmline, as reported by Davies et al. (1998), andthe Brγ 2.17 µm line. Because these lines arenarrow and show ordered rotation, it is like-ly that they arise in a disc around the AGN.The position angle and speed of the rotationare consistent with those at larger radii, indi-cating that down to scales of a few parsecsthere is no warp in the galactic plane.Circinus is known to exhibit a number ofhigh-excitation coronal lines. Of these, the[CaVIII] line at 2.32 µm (the ionisationpotential of which is 127 eV) is particularly

strong. An initial analysis of the line proper-ties reveals an increase in the velocity anddecrease in its dispersion from the nucleus toa region offset to the northwest. Our inter-pretation is that there are two components tothis line: a broad component centred on thenucleus at the systemic velocity and proba-bly associated with the Broad Line Region;and a narrow component, which is redshift-ed by an additional 140 km/s, offset in thedirection of the prominent ionisation cone,and likely associated with it.

NGC 7469 is a prototypical Seyfert 1galaxy at a distance 66 Mpc that is wellknown for its circumnuclear ring, as well asa significant contribution from star forma-tion to the nuclear luminosity (e.g. Genzel etal. 1995). Recent adaptive optics long-slitspectra combined with a millimeter interfer-ometric map of the cold gas (Davies et al.2004) led to a dynamical model in which thegas forms two rings, at 2.5) (800 pc) and 0.2)(65 pc). In this interpretation, the nuclearstar forming region, which contributes atleast half of the mass within 30 pc of thenucleus, was confined within the inner ring.These results are confirmed by new datafrom SINFONI which reveal the full 2-


Figure 13: The Circinus galaxy - the near-est galaxy with an active centre (AGN) -was observed in the K band (2 µm) usingthe nucleus to guide the SINFONI AO-Module. The seeing was 0.5 arcsec and thewidth of each slitlet 0.025 arcsec; the totalintegration time on the galaxy was 40 min.At the top is a K-band image of the centralarcsec of the galaxy (left insert) and a K-band spectrum of the nucleus (right). In thelower half are images (left) in the light ofionised hydrogen (Brγ) and molecularhydrogen (H2) lines, together with theircombined rotation curve (middle), as wellas a CO 2-0 bandhead map, which tracescool stars in the nucleus, and images ofbroad and narrow components of the high-excitation [Ca VIII] spectral line (right). Thefalse colours in the images representregions of different surface brightness.

Figure 14: NGC 7469 was observed inK band (2 µm) using the nucleus as the

wavefront reference for the adaptiveoptics and with slitlet widths of 0.025).

At the time of the observations theseeing was 1.1). The total integrationtime on the galaxy is 1 hour 10 min.

Upper left: image of the K-band con-tinuum in the central arcsec of NGC

7469. Upper right: a spectrum extract-ed from the nucleus. Lower left: image

of the molecular hydrogen line togetherwith its rotation curve. Lower centre:

image of the Brγ line. Lower right:image of the CO 2-0 absorption band-

head which traces cool stars.

dimensional distributions of the H2 1–0 S(1)line and the nuclear star forming region,through the CO 2–0 bandhead.

A PA PAIRAIR OFOF SSTTARAR-F-FORMINGORMING

GGALAXIESALAXIES AATT ZZ=2=2It is becoming increasingly clear that mostof the baryonic mass in galaxies was put inplace between about 8 and 11 billion yearsago (redshifts between 1 and 3). However,the real test of our understanding of galaxyformation and evolution is not just when themass accumulated, but rather: How did itaccumulate? Did mass assembly occur in thesame way in different types of galaxies (i.e.,spiral galaxies like the Milky Way and ellip-tical galaxies)? Was the mass accumulationrate mass-dependent so that more massivegalaxies formed earlier in the history of theUniverse? Why do some galaxies have largeamounts of angular momentum, while othersdo not?

To address these questions, astrophysi-cists in Europe and the US have definedsamples of galaxies that are at redshiftswhere most of the mass was likely put inplace, namely around 2. For example,Steidel and collaborators have defined selec-tion criteria based on three optical colourswhich efficiently select actively star-form-ing galaxies at redshifts between 1.5 and 2.5(the so-called “BM and BX galaxies”;Steidel et al. 2004). Galaxies selected thisway are forming stars at approximately20–60 M0/yr, appear to be substantiallyevolved with stellar masses of about1011 M0 and have approximately solarmetallicity. All these properties suggest thatthey are highly evolved systems, eventhough their star-formation rates are sub-stantial. In contrast, they tend to have com-plex UV morphologies and their dynamicalproperties are confusing – typical forgalaxies that are rather unevolved.Interestingly, BM/BX galaxies with elongat-

ed, sometimes flattened morphologies likethose usually associated with discs, appearto have smaller line widths than galaxies ofmore irregular shape. Erb et al. (2004)hypothesized that these galaxies are in thecourse of a merger, and not showing signs ofsystematic rotation which would be associat-ed with a disc.

It is this last argument that led us tocarry out observations with SINFONI of apair of BX galaxies – BX 404/405 – duringcommissioning. Since the morphologies ofBM/BX galaxies are complex and the mostextended structures are not necessarily dueto coherent rotation but to companion merg-ing galaxies, it is difficult or even impossibleto define the “kinematic major axis” (theangle along which the velocity change orgradient reaches its maximum). ExploitingSINFONI's integral field capability, onedoes not a priori have to choose a positionangle, but simply puts the target in the fieldof view and then measures the source kine-matics. If for example a system consists of apair of merging galaxies, then there mighteven be two or more velocity components:Each galaxy could show a rotation curve ofits own inclined by a different angle, andsuperimposed on the relative velocity alongthe line connecting the two galaxies. Withsuch complicated objects, SINFONI is par-ticularly powerful in determining the natureof the sources by obtaining the complete pic-ture of the dynamics at once.

The galaxies BX 404 and 405 are espe-cially interesting because this is an associa-tion of two star-forming galaxies at almostexactly the same redshift only about 3–4 arcseconds apart (about 30 kpc at this redshift).Thus we could cover both objects in a singlepointing. What we found is fascinating: therelative velocity of BX 404 and 405 is onlyabout 150 km/s. They are separated by about30 kpc, while the emission-line object to thesouth and west of BX 404 and 405 has a

velocity of 150 km/s relative to BX405 andabout 300 km/s relative to BX404. The twocomponents of BX405 have velocities thatdiffer by about 70 km/s, with a spatial sepa-ration of about 6 kpc. The velocity and sizeallow us to roughly estimate that BX405 hasa dynamical mass of about 1010 M0.

The overall similar velocities in this sys-tem suggest that this may be an interactingset of galaxies, which could merge to form asingle more massive object. If BX 404 and405 are part of a larger gravitationally boundstructure, their relative velocities and pro-jected distances suggest a total mass ofabout 1011 solar masses. In addition, theratio of [NII]/Hα can be used to give a crudeestimate of the gas-phase metal abundances.In BX 404, the [NII]/Hα line indicates atotal metallicity similar to the Sun. We onlyhave an upper limit for BX405, suggestingthat its metallicity is less than that of BX 404and the Sun.

Obviously, these results are only a firststep: before any robust statement can bemade, a statistically significant sample ofsuch high-redshift galaxies will have to beobserved. Nonetheless, these observationsillustrate the great promise of SINFONI forobtaining a detailed picture of the propertiesof star-forming galaxies in the high-redshiftUniverse.

RREFERENCESEFERENCESH. Bonnet et al. 2003, SPIE 4839, 329F. Eisenhauer et al. 2003, Proc. SPIE 4844, 1548 M. Tecza, et al. 2002, Proc. SPIE, 4842, 36Davies et al. 1998, MNRAS, 293, 189 Davies et al. 2004, ApJ, 602, 148Erb et al. 2004, accepted for publication ApJ

(astro-ph/0404235)Genzel et al. 1995, ApJ, 444, 129Genzel, R. et al. 2003a, ApJ 594, 812Genzel, R. et al. 2003b, Nature 425, 934Ghez, A. et al. 2003, ApJ 586, L127Schödel, R. et al. 2002, Nature 594, 812Steidel, C. C. et al. 2004, ApJ, 604, 534

The Messenger 11724

Figure 15: Image of theGalaxy pair BX 404/405 (red-

shift 2.03) in the light of theHα recombination line (rest-frame wavelength 656 nm).

One of the spectra (upperright) clearly reveals signs of

a velocity shear while theother does not. Such shearmay be a sign of rotation, apossible signature of a disc

galaxy – or of a merger. Therelatively small velocity offsets

of the galaxies suggest thatthey are interacting and may

perhaps merge to form amassive galaxy.


IIN JULY of this year the MACAOteam returned to Paranal for the thirdtime to install another MACAO-VLTI system. These are 4 identical60 element curvature adaptive optics

systems, located in the Coudé room of eachUT whose aim is to feed a turbulence cor-rected wavefront to the VLTI Recom-bination Laboratory. This time the activitiestook place on Yepun (UT4). The namingconvention has been to associate theMACAO-VLTI number to the UT numberwhere it is installed. Therefore, although wespeak here of MACAO#4, it is the third sys-tem installed in Paranal.

This short note will summarize the sta-tus of the MACAO-VLTI project, put for-ward a few results obtained recently andpoint out that with 3 operational MACAO-VLTI AO systems in Paranal, phase closurecan now be attempted using AMBER fedwith 3 AO corrected beams.

TTHEHE AADVDVANTANTAGESAGES OFOFSSERIALERIAL PPRODUCTIONRODUCTION

The opportunity of producing a series ofinstruments is not given to all, and this isunfortunate. We could not emphasizeenough the advantages of such strategy.MACAO benefited from this situation fromthe start of the project all the way to the endat the commissioning activities.

For the ESO Adaptive OpticsDepartment the standardization of severalinstruments presented numerous advan-tages: four (4) MACAO-VLTIs plus onespare, SINFONI and CRIRES. To name afew of these advantages:• Similar concepts for the design documents,• Optimization of staff efforts,• Single procurement and acceptance for all

units (in general 7 units),• Great flexibility and margin during accept-

ance and integration of first systems; ifsome of the 7 units are not acceptable,others are and allow to pursue theassembly/integration activities,

• Compatibility among MACAO, SINFONI,CRIRES allowing exchange of compo-nents (during the whole life of theproject),

• Large flexibility for improving the systemperformance. Basic specifications/func-tionalities were fulfilled for the first sys-tems and became better as the teamacquired a deeper understanding of itsfunctioning.

• Repeated and improved assembly/integra-tion procedures, test procedures (PAE)and commissioning activities

Similar benefits, of course, came fromthe serial production of the VLT UnitTelescopes.

MACAO#4 (UT4)MACAO#4 (UT4)CCOMMISSIONINGOMMISSIONING

In 2003 the first and second MACAOs (UT2and UT3) were commissioned in April andAugust respectively. A press release (ESOPR/11 03; 13 May 2003) was published topresent the first light results. In November ajoint effort between the AO dept. and VLTIused 3 nights on sky to characterize the gain

TTHIRDHIRD MACAO-VLMACAO-VLTI CTI CURURVVAATURETURE

AADAPTIVEDAPTIVE OOPTICSPTICS SSYSTEMYSTEM NOWNOW INSTINSTALLEDALLED

R. AR. ARSENAULRSENAULTT 11, R. D, R. DONALDSONONALDSON 11, C. D, C. DUPUYUPUY 11, E. F, E. FEDRIGOEDRIGO 11, N. H, N. HUBINUBIN 11,,L. IL. IVVANESCUANESCU 11, M. K, M. KASPERASPER 11, S. O, S. OBERBERTITI 11, J. P, J. PAUFIQUEAUFIQUE 11, S. R, S. ROSSIOSSI 11, ,

A. SA. SILBERILBER 11, B. D, B. DELABREELABRE 11, J.-L. L, J.-L. L IZONIZON 11, P, P. G. GIGANIGAN 22

1EUROPEAN SOUTHERN OBSERVATORY (ESO)2LESIA, OBSERVATOIRE DE PARIS-MEUDON, FRANCE

Figure 1: An impressive result of the August’03 commissioning; an image ofNeptune in H-band (Van Cittert deconvolved). Besides the spectacular resolutionof the atmospheric bands, this picture illustrates the capability of MACAO-VLTIto correct the wavefront on extended objects. The angular diameter of Neptuneis 3 arcsec and the width (FWHM) of the narrowest bands is 67 mas.

of using VINCI with the MACAO-VLTIs.Results of these various activities can befound in Arsenault et al. (2002, 2004a,2004b), and Wittkowski et al. (2004). Ageneral description is also provided in theAdaptive Department web pages at:http://www.eso.org/projects/aot/

The commissioning activities of thisMACAO system were reduced to a mini-mum given the small number of nights onthe sky (3) due to the busy UT schedules.Given the success of the previous commis-sioning on UT2 and UT3, this appeared to bea low risk strategy.

In July (2004) the Tip-Tilt Box on UT1was decommissioned and some componentsre-used to integrate the UT4 MACAO-VLTIsystem. The commissioning went smoothly,especially the re-assembly/integrationphase. It was completed early and the cali-brations could start several days before theon-time sky.

The loop was closed on July 29th,approximately one half hour after the objectwas acquired. Usual verifications were per-formed: star acquisition, off-axis acquisitionwith XY table, atmospheric refraction com-pensation (for different guiding and scientif-ic wavelength), chopping algorithm test,throughput of the system, performance onbright star etc.

Only after these tests were completedwas the faint star performance of MACAOcharacterized. The results are summarized inFigure 2. A V~15.7 magnitude star was

acquired, adaptive optics correction opti-mized and a K-narrow band image wastaken. Strehl and FWHM were measured.The star was then dimmed artificially byinserting a neutral density filter in the beam.The faintest equivalent magnitude reachedwas V ~19.8 (K-type star) but this value canvary depending on whether the star is red orblue. For a G-type star one should expect asimilar performance for V~18 magnitude.The inconvenience of this method is that thesky background is also dimmed by the neu-tral density filter, but we believe that the factthat this test was carried out by full mooncompensates for this effect.

During this particular run UT2 and UT3systems went through a software upgrade inorder to have similar configurations on allthree MACAOs.

MACAO-VLMACAO-VLTI TI SSUMMARUMMARYY OFOF PPERFORMANCEERFORMANCE

The critical specifications for MACAO-VLTI are few: strehl ratio versus guide starmagnitude, artificial piston over the pupilintroduced by the deformable mirror.

The K-band strehl ratio specificationsfor MACAO-VLTI are 50% for stars V<11and 25% for V=15.5 in seeing conditions of0.65). In 0.8) seeing MACAO has obtainedstrehl ratios >50% for bright sources(V<11.5) even 60% if one corrects for theimperfect strehl of the test camera (typically~90%). On fainter stars the strehl ratioremains larger than 25% until V~16; howev-

er performance can deteriorate for a blueobject of V~16 (Avanlanche Photodiodeshave a peak of sensitivity at ~0.7 µm).

The piston specification of 25 nm RMSin a 48 msec time window has always beenvery critical; progress has been made recent-ly allowing us to fulfill this very challengingrequirement. The improvements leading tothis are:• Control frequency of 420 Hz rather than

350 Hz; important decrease in the exci-tation of the deformable mirror main res-onances

• Improvement in the control matrix andhigher accuracy of the interaction matrixmeasurement

• Taking into account the non-linearity ofthe deformable mirror at large stroke.

In conclusion the MACAO VLTI instal-lations and commissioning activities are pro-ceeding according to schedule and theresults are extremely encouraging showingperformance better than expected and a highsystem robustness. The fourth and lastMACAO will be installed in the course of2005.

RREFERENCESEFERENCESR. Arsenault et al., 2002, SPIE proc. 4839, p.174R. Arsenault et al., 2003, ESO Messenger 112, 7R. Arsenault et al., 2004a, SPIE proc. 5490R. Arsenault et al., 2004b, SPIE proc. 5490M. Wittkowski, P. Kervella, R. Arsenault, 2004,

A&A 428, L39

The Messenger 11726

Figure 2: MACAO#4(UT4) commissioningresults (self-explana-tory).


VVISTA (Visible and Infrared Survey Telescope forAstronomy) is the result of a 1998 application, tothe UK’s Joint Infrastructure Fund, by the VISTAConsortium of 18 UK Universities (see acknowl-edgments) for funding for a 4-m wide field survey

telescope, which was approved in summer 1999. The purpose ofthe wide field (1.65o diameter in the IR) survey telescope and cam-era facility is to perform extensive surveys of the southern skieswhose sensitivity is matched to the needs of today’s 8-m class tel-escopes. Imaging surveys not only generate much science directlybut also are needed to efficiently choose objects for further studyby the VLT. IR surveys particularly target the cold universe, theobscured universe, and the high redshift universe.

The VISTA Consortium used competitive tendering to choosethe UK Astronomy Technology Centre (UKATC) in Edinburgh totake on the technical responsibility for design and construction anda VISTA Project Office was accordingly set up. Their preliminaryconceptual design studies resulted in Technical Specifications andStatements of Work for various work packages, which wereawarded through a process of open competitive tenders. Afterinvestigating various potential telescope sites in Chile, and discus-sions with the site sponsors, the VISTA Consortium decided thatthe Cerro Paranal Observatory was the best site for maximizingthe survey speed of VISTA. Interestingly this decision by theVISTA Consortium helped considerably in bringing about the sub-sequent decision by the UK to join ESO. As an ESO telescope,VISTA and its large surveys will now be fully exploited by thewhole ESO community. This article provides an overview of someaspects of the system.

DDESIGNESIGN DRIVERSDRIVERSThe purpose of VISTA is to survey both spatially and over time,through monitoring. Good image quality is required both to

TTHEHE VVISIBLEISIBLE &&IINFRAREDNFRARED SSURURVEYVEY

TTELESCOPEELESCOPE FORFOR

AASTRONOMYSTRONOMY

VISTA’S 4-METRE PRIMARY MIRROR AND 1.65-DEGREE DIAMETER INFRARED FIELD OF VIEW FEEDS A 64MEGAPIXEL (0.34) PIXEL) CAMERA. RAPID DEEP IR (0.85–2.3µm) IMAGING SURVEYS WILL BOTH SELECT

OBJECTS FOR FOLLOW-UP WITH THE VLT, AND DIRECTLY STUDY A WIDE VARIETY OF ASTRONOMICAL TOPICS.

J.PJ.P. E. EMERSONMERSON 11, W, W.J. S.J. SUTHERLANDUTHERLAND 22, A.M. M, A.M. MCCPPHERSONHERSON 33, , S.C. CS.C. CRAIGRAIG 33, G.B. D, G.B. DALALTONTON 44 & A.K. W& A.K. WARDARD 44

1ASTRONOMY UNIT, QUEEN MARY UNIVERSITY OF LONDON, UK 2INSTITUTE OF ASTRONOMY, CAMBRIDGE, UK

3UK ASTRONOMY TECHNOLOGY CENTRE, EDINBURGH, UK4RUTHERFORD APPLETON LABORATORY, CCLRC, DIDCOT, UK

wwwwww.vista.ac.uk.vista.ac.uk

Figure 1: Drawing of VISTA telescope (camera not mounted).

enhance sensitivity and resolution, and tominimize confusion, leading to the require-ments for an excellent site and a pixel scalematched to sample at least the median seeingat the site. Good sensitivity is required (e.g.to go deep in a reasonable integration time,and to enable monitoring of faint objects)leading to a requirement for a 4-m diameterprimary mirror. To get statistical samples ofsky area/objects (for example to study intrin-sic scale sizes of clustering, to find rareobjects, and to generate the large samplesneeded to get accurate properties) largeareas must be surveyed, leading to a require-ment for a large field of view. Both near-IRand visible surveys were required.

The design of VISTA was thus driven bythe requirements of good image quality inboth the near-IR (0.5) fwhm) and visible andover a large (1.5–2.0o) diameter field ofview with a 4-m class telescope, togetherwith the ability to change between use of avisible or an IR camera. Finally, designtrade-offs were to be resolved wheneverpossible in favour of maximizing the surveyspeed (in square degrees/hour for a specifiedset of surveys taking into account the over-heads of changing filters, slewing, readingout etc) within the available financial budg-et. As the funding needed to build the visiblecamera is not yet available we focus here onthe IR, without forgetting that VISTA ispotentially an extremely powerful visible2.1o diameter survey telescope with 50 red-optimized 4096u2048 CCDs with 0.25)pix-els to complement the blue-optimized VST.

To turn the concept of survey speed intoa quantitative tool, the surveys that VISTAmight be expected to undertake were definedto assist the VISTA Project Office in opti-mizing VISTA for survey work. By examin-ing the science drivers the VISTAConsortium defined a Design ReferenceProgramme (Table 1) to match the scienceaims. Each survey is primarily defined by asolid angle of sky, a set of pass bands, and adetection limit to be reached in each passband. In addition monitoring programmesinvolve a number of repeat observations of

each field, and there is a goal of a southernsky atlas using the worst-quartile seeingtime over 4 years, this would cover thehemisphere in two bands to over 3 magdeeper than the 2MASS survey. [N.B. Thereis also a Y (1.02 micron) filter available, nar-row band filters could be purchased, and thedetector system would allow use of a zIR fil-ter.]

The surveys that VISTA will actuallyundertake remain to be decided, and willdepend on the properties of the final com-missioned system, progress in survey sci-ence by 2006, and the deliberations of theESO bodies that will determine the actualtime usage.

VISTA's strength, in addition to its spec-ifications, is that it is a survey machine withtime dedicated to ambitious, communallyplanned legacy programmes. The key, apartfrom the performance of VISTA itself, is todesign survey strategies that maximize theutility of the data to many different scienceprogrammes. Thus, for example, many sur-veys will likely be constructed in multiplepasses to enable completion of monitoring

programmes and some key fields will bemonitored over many years. VISTA is con-ceived as a blend of 75% of ‘public’ time(e.g. Schmidt-like sky surveys) used for pre-planned large survey and monitoring pro-grams together with 25% of competitively(traditional) based time.

DDESIGNESIGN CONCEPTCONCEPTTo cover large areas of sky rapidly enough toproduce timely results requires as large afield of view as possible. At the same timeoff-axis (and chromatic) aberrations over thelarge field must be kept down to a level thatdoes not much degrade the size of the stellarimages incident at the telescope. VISTAadopts an unusual design solution where theprimary and secondary mirror conic con-stants are optimised jointly with the IR cam-era lenses to optimise image quality over theentire field of view. This leads to a quasi-Ritchey-Chretien solution but with signifi-cant aberrations for the 2 mirrors alone. Thetwo mirrors provide most of the power of thesystem, whereas three lenses in theCassegrain camera act as a reasonably con-ventional field corrector mainly serving tocorrect the off axis aberrations, withoutintroducing much chromatic aberration, outto a field diameter of 1.65o (or 2.1o in thecase of the visible camera design). As thetelescope alone produces significant spheri-cal aberration and off-axis coma, it must beused with the camera to produce goodimages. (This leads to challenges in testingthe telescope and camera separately). The 4-m diameter primary is f/1 and with a 1.24-mdiameter secondary, the resulting beam atthe focal plane is f/3.26 producing 0.34) pix-els with the 20-micron pixel size of the IRdetectors. For pixels at either extreme of thelarge focal plane not to look off the primary,any individual pixel cannot use the entireprimary physical diameter. In fact any indi-

The Messenger 11728

Table 1: Design Reference Program for IR System Design.

Survey name AreaSq. deg

Limiting magnitude

Band J H Ks

Wide high galactic latitude 3000 21.2 20.0 19.5

Wide low galactic latitude 1500 20.5 19.5 19.0

Deep 100 22.8 21.5 21.0

Very Deep 15 23.8 22.5 22.0

Figure 2: Cutaway of opticalassemblies including cold mass.

vidual pixel in the focal plane uses 3.7-mdiameter of the primary. The f/1 primaryallows a relatively squat telescope that helpscontain construction costs, and delivers afast Cassegrain focus with an acceptablesecondary diameter. The curvature of theprimary is unusually high for such a largemirror.

The standard method of rejecting theunwanted IR background from telescopestructure, dome etc. in most IR instrumentsis to form an image of the pupil and to placea cold stop at that image to baffle out theunwanted background radiation. Thisensures that the detector “sees” only coldsurfaces inside the cryostat, the highlyreflective low emissivity telescope optics,and the sky being imaged. VISTA’s largediameter and large field of view, togetherwith the need to maintain image quality, ledto severe difficulties with cold stop designs,either using lenses (e.g. no IR glasses avail-able in ~600mm size and with the achromat-ic properties needed) or using mirrors (e.g.packaging and obscuration problems).VISTA’s solution (see Fig. 2) is to dispensewith the traditional cold stop, and incorpo-rate a long cold baffle at the front of thecamera to reduce the background on thedetectors. If the cryostat/baffle system islong enough, ensuring that the detectors seethe smallest possible solid angle out of thecryostat, and the secondary slightly under-

sized to form the system stop, the field ofview of all pixels is limited and does notoverlap the edge of the primary mirror, orsee other parts of the telescope structure.The cold baffle tube forward of the correctorcontributes negligibly to the background inthe focal plane.

There could however be an extra thermal

component due to emission from the sky(mainly OH) that enters around the second-ary mirror. This extra sky emission isblocked with a warm reflective annular(1.65-m) baffle around the (1.24-m) second-ary mirror, so all that the detectors see fromthis annulus is the reflection of the cold inte-rior of the camera. The result is that the total

© ESO - September 2004 29Emerson J.P. et al., VISTA

Figure 3: CrossSection of IRCamera Design.

Table 2: VISTA’s 1st VIRGO science detector properties.

ParameterFirst Science detector VM301-SCA-22 (72K)

Quantum efficiency71% (J)74% (H)75% (Ks)

Well depth 156 ke– (0.7 V bias)

Dark generation 1.7 e–/pix/sec

Read noise 17 e– (rms)

No. of outputs 16 outputs (1.001s)

Non-linearity 3.3% (100 ke– FW)

Pixel defects <1%

Flatness ~6 µm (p-v)

Conversion gain 3.58 µV/e–

Output DC level 3.23 V

Operability (%) 99.18%

Figure 4: Focal planelayout for IR camera.

background is limited to unavoidable ther-mal emission from the primary, secondary,spider, and cryostat window, plus a modestcontribution from the reflective baffle.Thermal contributions from the optics are ofcourse present whether or not a cold stop isused. Analysis shows the system deliversperformance certainly no worse than an(impractical) cold stop system would havedone.

IR CIR CAMERAAMERAThe camera includes the entrance window,cold baffle tube, lenses, filter wheel anddetectors and is being constructed by a con-sortium of Rutherford Appleton Laboratory,UKATC and Univ. of Durham (Dalton et al2004). A cross section is shown in Fig. 3.The cold baffle approach inevitably resultsin a large (950mm IR grade fused silica)entrance window which potentially deliversa large heat load to the cryostat, potentiallyrequiring a large number of closed cyclecoolers to maintain the required tempera-tures. The solution adopted is to coat thereflecting baffle surfaces in the cryostat witha selectively reflective coating with highreflectivity around 10 µm, where the thermalemission peaks, and good absorption below3 µm, where the detectors are sensitive, sothat much of the heat load is returned to thewindow. Normally the window should notbe subject to dewing or frosting, and meas-ures to prevent this during ambient condi-tions when it is a danger are designed in. Thebaffles and lenses are mounted in a tube sothat when mounted on the telescope thecamera protrudes through the primary. Theall-up camera system has a mass of 2900 kg.

The focal plane contains a sparse 4u4array of Raytheon VIRGO 2048u2048HgCdTe IR detectors (Love et al 2004) andwill be the largest IR focal plane ever built.The parameters of the first delivered sciencedetector are given in Table 2 as measured atthe UKATC. A specially developed versionof ESO’s IRACE controller will be used tosynchronously control the 16 VIRGO detec-tors (Bezawada et al 2004) .

As the detectors are not 4-edge buttable,some gaps are inevitable. Analysis hasshown that the most effective way to maxi-mize the survey speed, given the availablefield of view and detectors, was to space thedetectors by 90% of a detector width in one(X) direction and 42.5% of their width in theother (Y) direction (Fig. 4).

A single exposure with this focal planeproduces a 0.6 square degree ‘pawprint’ onthe sky, and other exposures must be used tofill in the gaps between the 16 detectors toproduce a contiguous image or ‘tile’ of skyof minimum size 1.5 degree u 1.0 degree.The simplest way to achieve this is with aseries of 6 suitably offset exposures (Fig. 5):first expose at position 1, then move up0.475 of a detector in Y to position 2 and

The Messenger 11730

Figure 5: Making a filled tile (c) from 6 pawprints (b) at various offsets (a). Each sky position isobserved at least twice.

Figure 6: Filter wheel schematic.

Figure 7: Diagramof telescope struc-ture showing themajor components.

expose, then up another 0.475 in Y to posi-tion 3 and expose, then move across 0.95 ofa detector in X to position 4 and expose, thendown 0.475 in Y to position 5 and expose,and finally down 0.475 in Y to position 6 forthe final exposure which completes the tile.This ensures each piece of sky is covered atleast twice, except for single exposures atthe upper and lower extremes in Y, whichwill find matching single exposures whenthe next tile is made.

Inspection of Fig. 4 also shows twofixed autoguider visible (red) CCDs (AG +Yand –Y). Only one chip will be used to auto-guide at any time, but a suitably bright guidestar may be chosen from either. A patrollingmechanism for acquiring a guide star wasrejected to minimize moving cryogenicmechanisms. There is also a curvature sens-ing device near each autoguider chip. Theseare used to feedback signals to the secondaryand mirror support to allow adjustments tomaintain the image quality.

Filters can be changed via a 1.37-mdiameter filter wheel (Fig. 6) which hasspace for 7 sets of 16 filters (each filters cov-ers one detector) and an (opaque) positionfor taking dark frames. The filter wheel alsocontains slots between the science filters forsets of auxiliary optics. These are occasion-ally used with the IR detectors in a wave-front sensing mode to monitor the figure ofthe primary, perhaps once just beforeobserving and once again during the night.

With 16 detectors, each 2048u2048,and 4-byte output, each pawprint will be268.4 Mbytes. Exposures are frequent in theIR so a typical night’s observing should pro-duce several hundred Gbytes of raw data. AsVISTA will be a dedicated survey facility,this leads to around 100 Tbytes per year.Processing this data rate requires very care-ful attention to standardizing data takingprocedures and calibrations.

TTELESCOPEELESCOPE & M& MIRRORSIRRORSThe telescope is an altitude azimuth designwith the azimuth axis above the primarymirror (Fig. 7). It will be produced byVertex-RSI, who have recently completedthe 4-m SOAR telescope on Cerro Pachon.

The f/1 primary zerodur blank was fig-ured to a meniscus shape of 17cm thicknessby Schott Glas (Fig. 8), and is being pol-ished by LZOS near Moscow, who also pol-ished the mirrors for the VST. The primary issupported on 84 active pneumatic axial and24 lateral pneumatic supports, the forces onwhich are controlled to ensure the mirrorkeeps its shape and position at various eleva-tions. The f/1 design keeps the telescope rel-atively short but a consequence of the fastprimary is that the image quality is very sen-sitive to the exact position of the secondarymirror. Therefore the results from the wave-front sensors near the focal plane are used toslowly adjust the position, tip and tilt of the

© ESO - September 2004 31Emerson J.P. et al., VISTA

Figure 8: Preparing the f/1 meniscus primary to leave Schott.

Figure 9: Telescope support base. The central column takes the azimuth encoder, the innerring is the pier on which the telescope itself will be supported, and the enclosure will sit on theouter wall. The VLT on Cerro Paranal can be seen in the background.

secondary by sending signals to a hexapodsecondary mirror support system providedby NTE SA of Barcelona.

SSITEITE & E& ENCLOSURENCLOSUREAs there was not enough space to fit VISTAon the Cerro Paranal summit as originallyenvisaged, the “NTT peak”, which is~1,500m north-east of the VLT, wasassigned to VISTA. By February 2003 thesummit was lowered by 5-m to a height of2518m to produce a ~4,000m2 platform onwhich to construct VISTA, and by June anasphalted road was constructed to the sum-mit. This was accompanied by conduits tohold the necessary electrical, communica-tions and other services needed at the sum-mit. In July 2004 the foundations for all thebuildings were in place and the circular baseon which the enclosure will sit was complet-ed (see Fig. 9).

The design of the enclosure is along sim-ilar principles to those of the VST to min-imise seeing effects due to the enclosure. Anauxiliary building will sit next to the enclo-sure to contain all the necessary equipmentand materials for maintenance. There isspace to store a second camera (if the visiblecamera is eventually funded) and someoffice space. The auxiliary building will alsocontain mirror washing and stripping facili-ties, and a coating plant. This has been con-tracted to Stainless Metalcraft, and will becapable of coating with protected silverbecause of its lower IR emissivity than tradi-tional aluminium. Both the enclosure andauxiliary buildings are contracted to EIE(Mestre, Italy) who are also responsible forthe enclosure for the VLT Survey Telescope.

EEXPECTEDXPECTED PPERFORMANCEERFORMANCETable 3 gives the anticipated 5σ 15 minutemagnitudes on the Vega scale for photome-try at 1.2 airmass in a 1.6 arcsec diametersoftware aperture, for a median site seeing of0.66) at 0.5µm, using the predicted systemperformance with protected silver coated

mirrors, and assuming the given sky bright-ness and atmospheric extinction.

The survey speed actually achieved forlarge-area surveys depends on the limitingmagnitudes sought, the detailed observingstrategy used and the overheads for the vari-ous dithers, steps and readouts, and controlactivities needed. For large-area surveys thecombination of VISTA’s collecting area andfield of view will make it the world’s leadingfacility for large-area near-IR surveys from2007.

AACKNOWLEDGMENTSCKNOWLEDGMENTSWe thank: the Office of Science and Technologyand the Higher Education Funding Council forEngland for funding through the JointInfrastructure Fund; the Particle Physics andAstronomy Research Council for additionalfunds; the Particle Physics and AstronomyResearch Council and their UK AstronomyTechnology Centre for organizing the realizationof VISTA through the VISTA Project Office, andESO for providing the site and advice. None ofthis could have been achieved without the help ofmore than 50 people from the 18 ConsortiumUniversities, ESO, and PPARC establishmentswho continue, with others, to work for the realiza-tion of VISTA, and who are too numerous toacknowledge individually.

VISTA is supported by a grant from the UKJoint Infrastructure Fund to Queen MaryUniversity of London on behalf of the 18University members of the VISTA Consortium of:Queen Mary University of London; Queen'sUniversity of Belfast; Universities ofBirmingham; Cambridge; Cardiff University;Universities of Central Lancashire; Durham;Edinburgh; Hertfordshire; Keele University;Leicester University; Liverpool John MooresUniversity; Universities of: Nottingham; Oxford;St Andrews; Southampton; Sussex; andUniversity College London.

RREFERENCESEFERENCESAtad-Ettedgui E. & Worswick S., 2002, Proc.

SPIE 4842-21.Bezawada N., Ives D., & Woodhouse G., 2004,

Proc. SPIE 5499-03.Craig S. et al., 2003, Proc. SPIE 4837, 178.Dalton G. et al., 2004, Proc. SPIE 5492-34.Emerson J., & Sutherland, W., 2003, Proc. SPIE

4836, 35.Love P.J. et al., 2004, Proc. SPIE 5499-08

The Messenger 11732

IR camera Band Y J H Ks

Assumed Sky Brightness mag /arcsec 17.2 16.0 14.1 13.0

Assumed Extinction coefficient mag /airmass

0.05 0.1 0.08 0.08

Sensitivity 5σ 15 min limiting (Vega=0) mag 22.5 22.2 21.0 20.0

Table 3: Anticipated performance with IR camera.

ALMA NALMA NEWSEWS

TT. W. WILSONILSON

The first edition of the European

ALMA newsletter is now available at:

http://www.eso.org/projects/alma/newsletter/This contains information about

progress in the planning and construction

of the Atacama Large Millimeter Array. A

staff consisting of Carlos De Breuck,

Martin Zwaan, and Tom Wilson assem-

bles and edits project information. The

newsletter will appear quarterly, so the

next edition will appear in October 2004.

In the the first edition are short

descriptions of: the ALMA Construction

site near San Pedro de Atacama; the

ALMA Regional Centers (ARCs); new

personnel; the current state of the antenna

selection process; the plans for ALMA

community day (Sept 24, 2004, in

Garching); and upcoming events.

The newsletter can be viewed as a

web page or can be downloaded as a PDF

file. You can also add yourself to the

mailing list by sending an email to:

[email protected] with “subscribe

alma-newsletter” in the first line of the

body. You will then receive email

announcements when new editions

become available.

LLAA SSILLAILLA NNEWSEWS

L. GL. GERMANYERMANY

It is with a very heavy heart that I

have had to bid farewell to La Silla after

my four years there as an ESO fellow. I

have really enjoyed the work, my col-

leagues, and meeting a substantial frac-

tion of the European observational com-

munity during that time.

Arriving to fill the service queues at

the 2p2m is a new OPA, Mauro Stefanon.

Mauro is not a stranger to La Silla

Observatory – he was involved in setting

up the REM project. We welcome him

back and wish him well for his year as

part of SciOps.


IIn collaboration with instrument con-sortia, the Data Flow SystemsDepartment (DFS) of the DataManagement and OperationDivision is implementing data

reduction pipelines for the most commonlyused VLT/VLTI instrument modes. Thesedata reduction pipelines have the followingthree main purposes:• Data quality control - pipelines are used to

produce the quantitative informationnecessary to monitor instrument per-formance.

• Master calibration product creation -pipelines are used to produce master cal-ibration products (e.g. combined biasframes, super-flats, wavelength disper-sion solutions).

• Science product creation - using pipeline-generated master calibration products,science products are produced for sup-ported instrument modes(e.g. combined ISAAC jit-ter stacks; bias-corrected,flat-fielded FORS images,wave leng th -ca l ib ra tedUVES spectra). The accura-cy of the science products islimited by the quality of theavailable master calibrationproducts and by the algo-rithmic implementation ofthe pipelines themselves. Inparticular, adopted automat-ic reduction strategies maynot be suitable or optimalfor all scientific goals.

Even though the main focusof the pipeline recipe develop-ment has been, and remains,VLT science operation support,ESO is endeavoring to releaseall operational instrumentpipelines to the community asrapidly as possible. Instrumentpipelines consist of a set of dataprocessing modules that can becalled from the command line,from the automatic data man-agement tools available onParanal or from Gasgano.

Gasgano is a data manage-ment tool that has been avail-

able on Paranal and as a desktop applicationfor several years. It simplifies the dataorganization process and allows file classifi-cation tasks such as: “What kind of data amI?”, e.g. BIAS, “to which group do Ibelong?”, e.g. to a particular ObservationBlock or template. Gasgano also makes theassociation of appropriate calibration fileswith science frames easier. The next logicalstep in the development of Gasgano was toextend its functionality to allow pipelinerecipes to be executed directly on a set ofuser selected files. This upgrade has beencompleted by the DFS in the past year.

In addition to extending Gasgano, DFShas also started the development of a set ofpipeline recipes for the IFU mode ofVIMOS. The main requirements were todevelop recipes which could be executed ina robust and automatic way, to support allexisting grisms, to provide the operational

teams with the information required toassess the quality of the observations and thehealth of the instrument and, last but notleast, to be Gasgano compliant enablingastronomers to reduce their own data at theirhome institute. The first release of the IFUrecipes has been operational on Paranalsince May 2004.

In the middle of July 2004, the VIMOSpipeline recipes, including IFU support aswell as imaging and MOS componentsbased on the code delivered by the VIRMOSconsortium, were released to the publictogether with Gasgano and are available forthe community from the ESO web site as abundled package.

The following sections summarise thetechnical capabilities of the Gasgano inter-face and provide an overview of the reduc-tion strategy adopted by the pipeline recipesfor the processing of VIMOS IFU data.

GGASGANOASGANO & ESO VIMOS P& ESO VIMOS PIPELINEIPELINE RRELEASEDELEASED

CCARLOARLO IIZZOZZO 11, N, NICKICK KKORNWEIBELORNWEIBEL 11, D, DEREKEREK MMCC KKAAYY 1,21,2, , RRALFALF PPALSAALSA 11, M, MICHELEICHELE PPERONERON 11, M, MARKARK TTAAYLORYLOR 33

1DATA MANAGEMENT AND OPERATIONS DIVISION, ESO2RUTHERFORD APPLETON LABORATORY, DIDCOT, UK

3STARLINK, BRISTOL UNIVERSITY, UK

Figure 1: Gasgano main window and recipe panel. A set of IFU frames are loaded into the main panel.The recipe panel is opened with the recipe vmifuscience loaded. A science exposure is being processedusing a number of calibration frames. The resulting log file is displayed at the bottom of the panel.

GGASGANOASGANOGasgano provides a means to automaticallyidentify and classify FITS files (e.g. BIAS,FLAT, SCIENCE). Classification rules forthe VLT instruments are part of the distribu-tion package. Gasgano also automaticallygroups files located on a specified set ofdirectories in a tree structure based on theRun ID and Observation ID of the files aswell as additional instrument specific key-words. Gasgano allows the user to view andsearch all the relevant information in a fileand displays FITS files and keyword valuesfrom the headers, and it provides the userwith an interface to pipeline recipes. Theuser selects the file(s) to be reduced and theappropriate recipe, launches the recipe paneland configures the execution of the datareduction procedure by entering parameters.The recipe can be executed directly from thepanel, the log files reviewed and the gener-ated products visualized. Figure 1 shows themain Gasgano window as well as the recipepanel after loading a VIMOS data set andselecting the vmifuscience recipe.

VIMOS IFU VIMOS IFU PIPELINEPIPELINE RECIPESRECIPESThe VIMOS IFU pipeline consists of twomain recipes, vmifucalib and vmifuscience,to process calibration and science datarespectively. The recipe vmifucalib deter-mines the spectral extraction mask, the dis-persion solution and the fibre relative trans-mission correction. The results of this recipeare used by the recipe vmifuscience which inturn produces the extracted, wavelength cal-ibrated and transmission corrected science

spectra, plus an image of the field of view ofa single VIMOS quadrant reconstructedfrom the extracted spectra by integratingover a predefined wavelength range.

For a complete processing of a scientificIFU exposure, three types of data arerequired by the pipeline: one or more flatfield lamp exposures, an arc lamp exposure,and a science exposure.

In addition the software assumes thatflat-fields and arc-lamp exposures areobtained almost simultaneously, withoutmoving the instrument between exposures.This is to ensure that the spectral extractionparameters obtained by processing the flat-field exposures are still valid for the arc-lamp exposure and can be applied directly.

The spectral extraction mask is createdfrom the flat-field exposure by identifyingthe spectra, i.e. the association of a spectrumon the CCD with a particular fibre and thesubsequent tracing of the spectra along thedispersion direction on the CCD. The fibres

are identified using a cross-correlation tech-nique which requires a preexisting and certi-fied fibre identification as reference.Tracing the spectra is also used to determinedead fibres (a fibre which cannot be traced isconsidered dead). The spectral trace is mod-eled by a low order polynomial. The accu-racy of the tracing is typically 0.01 pixel.

The spectral extraction is based on anempirical spectral profile which has beenconstructed by examining the half-profilesof the first and last spectrum of each 80fibres block of each pseudo-slit. The largergap between the last fibre of a block and thefirst fibre of the next one allows the determi-nation of the profile down to the backgroundlevel. Because of the spectral curvature, adifferent sampling of the fibre profile isavailable at different positions along the dis-persion direction. An example of such aempirical spectral profile is shown in Fig. 2.The obtained profile shows a negligiblecolour dependency (less than 2%); however,

The Messenger 11734

Figure 2: Data (about 24000pixel values) from which the

empirical fibre profile hasbeen constructed for one

fibre spectrum obtained withthe HR_orange grism

Figure 3: Raw spectra (left)of an IFU observation (quad-rant two) obtained using thehigh resolution grismHR_red. The dark area onthe left is due to the lowertransmission of those fibres.The extracted spectra (topright) has been wavelengthcalibrated and corrected forthe relative fibre transmis-sion effects. The noisy areaat the bottom of the imagecorresponds to the darkarea on the left of the corre-sponding raw image. Thereconstructed image (bot-tom right) is also a productof the pipeline


profiles obtained from different fibres showdifferences, which may, in the future, betaken into account by a parameterised modelof the profile. The currently implementedspectrum extraction algorithm uses only thevalues of the 3 pixels closest to the fibre cen-troid position, corrected for the profile shapeand averaged, since up to 1.5 pixels from thecentroid position, the cross-talk contamina-tion by nearby fibres can be neglected.

The wavelength calibration is carriedout on the extracted arc-lamp spectra. Forhigh and medium resolution spectra an accu-racy of 0.2 pixels is achieved, while for lowresolution spectra the accuracy is approxi-mately 0.5 pixels because of the multiplex-ing of spectra which leads to systematicerrors due to the contamination of adjacentspectra along the dispersion direction.

When science observations areprocessed the spectral extraction mask isaligned to the science exposure using thebrightest spectra in the science exposure as areference. This compensates for changes inthe positions of the science spectra on theCCD with respect to the positions of the flat-field spectra. Offsets along the dispersiondirection are corrected by adjusting the dis-persion solution computed by vmifucalib tothe position of the selected sky lines. Usinga single spectrum of the science exposure issufficient to achieve a mask alignment accu-racy of 0.1 pixel for all fibres. With a fibre-to-fibre distance of about 5 pixels in the

direction perpendicular to the dispersion,there is a maximum displacement of about 2pixels in that direction that can be correctedfor. Should these displacements be larger(e.g. because of flexures due to a large rota-tion of the instrument or changes in themechanical configuration), the fibres maynot be correctly identified and the spectralextraction mask will not be correctlyaligned.

Finally the extracted science spectra arecorrected for the differences in the fibretransmission where the correction factor iscomputed from the flat-field spectra by inte-gration over a fixed wavelength range(avoiding the 0th order contamination in thecase of multiplexed spectra), normalised tothe median of these integrated fluxes. Therecipe vmifuscience does not currently applya flat-field correction to the extracted sci-ence spectra. Instead, the extracted flat-fieldspectra are provided as an additional prod-uct, which can be used for an approximateflat-field correction, if desired. Figure 3shows one quadrant of an IFU raw observa-tion, the extracted spectra as well as thereconstructed image produced by thepipeline.

A description of how the IFU recipes areused by the Quality Control group inGarching can be found at http://www.eso.org/qc under the VIMOS section.

GGETTINGETTING THETHE SOFTWSOFTWAREAREGasgano & the VIMOS recipes can bedownloaded together with user manualsfrom (www.eso.org/observing/gasgano/vimos-pipe-recipes.html). We look forward to theextensive use of these new data reductiontools among the community of investigatorswho have obtained VIMOS data. Your feed-back is welcome at [email protected] andwill help us to improve our tools.

AACKNOWLEDGMENTSCKNOWLEDGMENTSThe software package on which the VIMOSpipeline is based was developed by the VIRMOSconsortium and is still the foundation of the cur-rent ESO VIMOS imaging and MOS pipelines. Aversion of the IFU data reduction routines wasalso delivered by the consortium but not adoptedby ESO because it was not suitable for automaticpipeline processing of all supported configura-tions. In particular we would like to thank PaolaSartoretti (DMD) who has been extensively test-ing the pipeline recipes and was a continuoussource of good ideas for improving the algo-rithms. We are grateful to Sandro D’Odorico(INS) for useful advice and to Gianni Marconi,Stephane Brillant and Stefano Bagnulo (ESO-Paranal) for their patience, the very good collabo-ration and constant support. The feedback wereceived in numerous discussions with our “betatesters”, Martino Romaniello (DMD), MarkusKissler-Patig (INS) and Harald Kuntschner wasvery much appreciated. Valuable suggestions onIFU data reduction strategies were provided byEric Emsellem and Arlette Rousset-Pecontal(Centre de Recherche Astronomique de Lyon) andby Martin Roth (Astrophysikalisches InstitutPotsdam).

The Milky Way above La Silla. To the left is the decommisioned 15-metre dish of the Swedish-ESO Submillimetre Telescope (SEST), and on the right in the back-ground is the dome of the ESO 3.6-metre telescope, at the highest point of the mountain. The southern Milky Way is seen along the right border of the SEST andabove the 3.6 metre telescope. In the highly polished antenna dish of the SEST there is a upside-down reflection of the sky and the horizon behind the photogra-pher. The yellow area of light to the right is the reflection of the city lights of La Serena, about 100 km away and too faint to disturb observations of celestial objectshigh above La Silla. Photo: Nico Housen (ESO) – ESO PR Photo 27/04.

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The Messenger 11736

TTHEHE BBIRIRTHTH OFOF AA MMASSIVEASSIVE SSTTARAR

NEW RESULTS FROM ESO AND IRAM SUGGEST THAT MASSIVE STARS FORM IN THE SAME WAY AS THEIR LOW-MASS COUNTERPARTS. IN THE OMEGA NEBULA, A YOUNG STELLAR OBJECT OF MORE THAN TEN SOLAR

MASSES IS SURROUNDED BY A HUGE ROTATING DISC WITH AT LEAST 100 SOLAR MASSES OF GAS AND DUST.PART OF THE GAS THAT FALLS ONTO THE GROWING STAR IS EJECTED PERPENDICULARLY TO THE DISC,PRODUCING A BIPOLAR JET AND AN HOURGLASS SHAPED NEBULA.

RROLFOLF CCHINIHINI 11, V, VERAERA HHOFFMEISTEROFFMEISTER 11, S, STEFTEFANAN KKIMESWENGERIMESWENGER 22, M, MARKUSARKUS NNIELBOCKIELBOCK 11,,DDIETERIETER NNÜRNBERGERÜRNBERGER 33, L, L INDAINDA SSCHMIDTOBREICKCHMIDTOBREICK 33 & M& MICHAELICHAEL SSTERZIKTERZIK 33

1ASTRONOMISCHES INSTITUT, RUHR-UNIVERSITÄT BOCHUM, GERMANY2INSTITUT FÜR ASTROPHYSIK, UNIVERSITÄT INNSBRUCK, AUSTRIA

3EUROPEAN SOUTHERN OBSERVATORYRep

orts

fro

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TThere is general consensus thatstars condense from clouds ofgas and dust within a massrange from about a tenth to ahundred solar masses. The for-

mation of stars up to ten solar masses (1solar mass [M0] = 1.989 u 1033g) can beexplained by the gravitational collapse of acloud fragment and the subsequent accretionfrom the surrounding interstellar mediumonto a so-called protostar (Shu et al. 1987).The associated density enhancement of theorder of 108 implies that the protostarbecomes optically thick at some point andstarts to increase its temperature: the objectis on its way to becoming a low-mass hydro-gen burning star. Closely connected with theaccretion phase is the formation of a circum-stellar disc which provides the necessarymaterial and, eventually, the conditions forthe creation of planets and life. Anotherassociated phenomenon is a bipolar outflowof mass that expands perpendicularly to theplane of the disc and is believed to be adirect consequence of the accretion process.Most of the above theoretically expectedstages could be verified observationally, andas such the formation of low-mass stars is afairly well-understood process.

Theoretical considerations, however,show that the accretion scenario may workonly for stars of up to about 10 M0 (Wolfire& Cassinelli 1987). Beyond that, a massiveprotostar evolves so rapidly into a hydrogenburning core that its radiation pressure ontothe in-falling dust and gas can halt or evenreverse the accretion process, and thus canprevent the formation of stars of highermass. Details depend on the geometry of theparent cloud and on the physical propertiesof the dust grains. Given this theoreticallimit of 10 M0 and the observational factthat most massive stars are born in denseclusters where they occur as multiple sys-tems, it was suggested that high-mass starsmight be the result of the merging of lowermass stars (Bonnell et al. 1998). This merg-ing process requires extremely high stellardensities which have never been observed intoday’s star clusters, but which could haveexisted during their early history. Recently,theoretical calculations have shown that –depending on the original cloud mass andthe opacity of the grains – stars between 20and 40 M0 can in principle be formed viaaccretion through a disc (Yorke &Sonnhalter 2002).

Discriminating between both formationscenarios observationally is rather difficultdue to several reasons: first, high-mass starsare extremely rare objects. Second, massivestars are generally far away and deeply

embedded within dust clouds which dimin-ishes their light substantially. Third, theyusually occur in the centres of stellar clusterswhere source confusion is a major problem.Finally, their lifetimes are only a few millionyears and their early evolution is according-ly short. In particular, massive stars start thehydrogen burning process at a point wherethey still have not yet reached their finalmass. Thus, depending on the formation sce-nario, one either has to observe the mergingprocess between two or more young stars orone has to witness the accretion through adisc; both observations require high spatialresolution and kinematic information that isalmost impossible to achieve with presentday instrumentation.

LLOOKINGOOKING INTOINTO THETHE CRADLECRADLEThe Omega nebula (M 17) is a well-knownregion of star formation in our Galaxy(Chini & Wargau 1998) at a distance of 2200parsec (1 parsec = 3.086 u 1018 cm).Figure 1 is part of a three-colour infraredmosaic of the area which was the initialobservation leading to our investigation. Itconsists of 9 individual, partly overlappingfields at 1.25, 1.65 and 2.2 µm and wasobtained with the infrared camera ISAAC atthe ESO Very Large Telescope (VLT) inSeptember 2002. The composite imageshows a dense cluster of young stars embed-ded in clouds of gas and dust with unprece-dented detail and depth; several high-massstars, whose total energy output exceeds thatof our sun by almost a factor of 107 ionise

the surrounding hydrogen gas. Adjacent toits south-western edge, there is a cloud ofmolecular gas which is a site of ongoing starformation. Due to the sensitivity of ourmeasurements the molecular cloud waslargely transparent and the nebular emissionof the HII region could shine through thedust. Against this nebular background, wediscovered a tremendous opaque silhouette,associated with an hourglass shaped nebulaand surrounded by a larger disrupting dustenvelope. As we will show in the following,this object resembles theoretical predictionsof a newly forming high-mass star surround-ed by a huge accretion disc and accompa-nied by an energetic bipolar mass outflow.

TTHEHE ACCRETIONACCRETION DISCDISCAfter the discovery of the object, we appliedfor discretionary time in order to study themorphology of the system in more detail. InJune 2003 we obtained three extremelyrewarding hours with NAOS-CONICA atthe VLT; Figure 2 shows the correspondinghigh-resolution 2.2 µm image of the newobject. Due to the adaptive optics technique– which eliminates atmospheric turbulence –the morphology of the silhouette was nicelyresolved into two triangular shaped dustlanes that resemble a flared disc, seen nearlyedge-on. The disc has a diameter of about20,000 AU (1 astronomical unit [AU] =1.496 u 1013 cm) which is about 200 timesthe size of our solar system and by far thelargest circumstellar disc ever detected.When going from the centre towards itsouter edges the disc widens substantially.Using the background nebular light as ahomogenous source of illumination, theextinction and thus the column density ofinterstellar matter within the disc can be


Figure 2: High-resolu-tion adaptive optics2.2 µm image of theaccretion disc. Thefield size is about 7 u7 arc seconds; theeffective spatial reso-lution is about 0.057arc seconds. The discsilhouette is seen inabsorption against thebright background ofthe HII region; thewhite contours delin-eate the densest partsof the inner disc. Abipolar outflowemerges from thecentral object. Theinsert shows the innerregion in more detailsuggesting that thereis an elongated – pos-sibly binary – sourceof about 450 u 250AU whose major axisis tilted by about 15degrees with respectto the disc axis.

FFFF Figure 1: Three-colour ISAAC mosaic of the star forming region M 17. The field size is about7 u 7 arc minutes, the effective spatial resolution is about 0.6 arc seconds; wavelengthcoding: blue 1.25 µm, green 1.65 µm, red 2.2 µm. A similar image from SOFI was releasedsome years ago as ESO-Press-Photo 24/00.

determined at each point along the line ofsight. The maximum column density ofhydrogen inferred from the optical depth at2.2 µm is ~ 6 u 1022 atoms cm–2; the associ-ated dust produces a visual obscuration of afactor of 1023 towards the central object.

Further physical properties concerningthe mass and the kinematics of the disc andits surroundings can be obtained from mil-limetre observations. We have observed theregion in molecular line transitions of sever-al CO isotopomeres like 12CO, 13CO andC18O and in the adjacent continuum at 1.3and 3 mm with the IRAM Plateau de BureInterferometer. The molecular spectroscopyindicates that the system rotates with avelocity of about 0.85 km/s at a radius of15,400 AU; its north-western part isapproaching the observer. From 13CO wederive a gas mass of at least 100 M0.

TTHEHE BIPOLARBIPOLAR NEBULANEBULAPerpendicular to the plane of the disc there isan hourglass shaped nebula visible through-out the entire spectral range from 0.4 to2.2 µm; Figure 3 shows a correspondingsequence of images, where the optical datahave been obtained with EMMI at the ESONTT. Obviously, the two nebular lobes showdifferent wavelength dependent intensities.The fact that optical light is detectablethroughout the huge amount of foregroundextinction can only be explained if the emis-sion is – at least partly – due to reflectedlight scattered by dust grains. The nebularlight consists of two separate components, adiffuse extended shimmer and a more com-pact emission in the central region.

Firstly, the diffuse emission – particular-ly prominent at optical wavelengths – issymmetric and seems to mark the walls of anhourglass shaped cavity. It extends at leastup to 5 u 1017 cm above the plane of the disctowards both sides with a maximum widthof about the same size (see Fig. 3.); theimage of the NE lobe is fainter and some-

what distorted by stray light from a nearbybright star. The emission of this hourglassfeature is due to scattered light from thewalls of a bipolar cavity that has probablybeen cleared by an energetic mass outflow.From the fact that the NE lobe becomesbrighter with increasing wavelength whilethe intensity of the SW lobe remains almostconstant we conclude that the former suffersfrom more extinction. This suggests an incli-nation of the disc of about 15 degrees withrespect to the line of sight which hides theNE lobe partly behind the disc. Vice versawe are facing the disc slightly from belowand thus are looking into the SW cavity. Thehourglass morphology of the SW cavity issupported by two curved dusty ejecta thatend in typical bow-shocks as a result of theirinteraction with the ambient medium. Thispicture is further corroborated by our COdata which, in part, also seem to trace thewalls of both cavities.

Secondly, there is a more compact emis-sion at both sides of the innermost disc. Bothblobs show strong wavelength dependencewith the western one being bright in the opti-cal and almost vanishing in the infrared; atabout 1 µm the clumps are of equal intensi-

ty and attain simultaneously their maximumbrightness. Beyond 1 µm the eastern blob isstronger by 10% at J and K and by 40% at H.This is in contrast to what one would expectfrom the extinction which is higher along theeastern line of sight due to the inclination ofthe disc. We therefore conclude that theremust be intrinsic intensity differencesbetween the two features which are mostprobably caused by an asymmetric outflow.Likewise, we speculate that additional lineemission contributes to the different mor-phological shapes.

The eastern outflow shows a pro-nounced morphology which is nicelyresolved by our adaptive optics image (Fig.2); it seems to originate close to the centralobject and resembles a precessing flow thatturns over shortly after leaving the inner-most region; farther out the orientation ofthe flow axis is almost parallel to the discplane. The much fainter western flow ismore diffuse and has an angle of about 45°with respect to the disc plane.

In order to explore the origin of the opti-cal nebula, we have taken spectra between0.4 and 0.9 µm that cover both cavities andthe flows (Fig. 4); the spectra were obtained

The Messenger 11738

Figure 3: Multi-colour sequence of thehourglass-shaped nebula. The changein morphology is displayed as a func-

tion of wavelength; the upper row wastaken at optical (0.44, 0.55, 0.78 µm),

the lower row at infrared (1.25, 1.65, 2.2µm) wavebands. In the upper row, thenebula is dominated by reflected light

from a bipolar cavity; the south-western(right) lobe is much stronger while the

north-eastern (left) lobe is obscured bythe disc. The lower row is dominated by

more compact emission from a bipolarjet (see also Fig. 2). Each frame has a

size of 30 u 30 arc seconds.

Figure 4: Optical spectrum of the bipolar nebula. The slit was oriented perpendicular to thedisc plane. The emission from the HII region has been subtracted by averaging several off-set positions. The various emission lines in the reflected light indicate evidence for ongoingaccretion.

in April/June 2003 with EFOSC2 at the ESO3.6 m and with EMMI at the ESO NTT. Theaccuracy of the wavelength calibrationallows sampling velocities down to 40 km/s.The spectrum is dominated by the emissionlines of Hα, the Ca II triplet 8498, 8542 and8662 Å, and He I 6678 Å which provideunquestionable evidence for an ongoingaccretion process (Hartmann et al. 1994,Muzerolle et al. 1998). Particularly the Hαline is extremely broad and shows a deepblue-shifted absorption as well as an inverseP Cygni profile; blue-shifted absorptioncomponents in permitted lines are typicallyassociated with accretion disc-driven out-flows (e.g. Calvet 1997). The same is truefor forbidden emission lines such as [O I]6300 Å and [S II] 6731 Å which are alsopresent in our spectrum. Numerous permit-ted and forbidden Fe II lines which arevelocity-shifted by ±120 km/s are clear sign-posts for high velocity dissociative shockswith velocities of more than 50 km/s. Recentspectroscopy with UVES in July 2004shows evidence for a variation in the Hαline; the line profile varies with time and asa function of the location across the lobes.Obviously, the infall and outflow of matter isnot a continuous process but the protostartakes a morsel of fuel every now and then.

TTHEHE NANATURETURE OFOF THETHE PROTOSTPROTOSTARARAs mentioned above, the disc is deeplyembedded in the molecular cloud probablybehind a visual extinction of about 50 mag-nitudes if we take the results from ourinfrared photometry for stars in the immedi-ate neighbourhood of the system as a guide-line. The dust within the disc producesanother contribution of about 50 magnitudestoward its centre which makes it impossible

to obtain any optical information about theaccreting protostellar object. Nevertheless,Fig. 2 shows an elongated 2.2 µm emissionfeature at the expected position of the form-ing star whose inclination is different fromthe orientation of the channel produced bythe outflow, i.e. from the inner gap of thedisc. One may speculate whether this elon-gated feature marks the starting point of theprecessing massive outflow or whether itoriginates from a binary system that is cur-rently born from a common accretion disc.NACO JHKLM measurements are sched-uled for the current period to clarify thenature of this object in more detail.Assuming that the central emission is due todirect stellar light we derive an absoluteinfrared brightness of K ~ –2.5 magnitudeswhich would correspond to a main sequencestar of about 20 solar masses and a tempera-ture of 35,000 K. An independent mass esti-mate from dynamical considerations, con-cerning the rotation of the molecular disc,yields a mass of about 15 solar masses forthe central gravitational object. Given thefact that the accretion process is still active,and that the gas reservoir of the disc stillallows for a substantial mass gain, we arguethat in the present case a massive protostar ison its way to becoming an O-type star.Theoretical calculations (Yorke &Sonnhalter, 2002) show that an initial gascloud of 60 to 120 M0 evolves into a starbetween 33 and 43 M0 while the remainingmass is ejected into the interstellar medium.

From all this evidence we conclude thata massive star is currently forming via accre-tion through a disc while the associatedenergetic mass outflow disrupts the sur-rounding environment and ejects part of theaccreted material into the ambient medium.

Our observations show – for the very firsttime – all theoretically predicted ingredientsof the star formation process directly andsimultaneously with a single object andtherefore improve our current understandingof such an event tremendously (Chini et al.2004). The schematic picture of Fig. 4 sum-marises the individual components asrevealed by our different observing tech-niques. A central protostar (maybe even abinary system), is surrounded by a flared,slowly rotating disc from which it accretesmass along a reconnected magnetosphericfield. A considerable fraction of the trans-ferred mass is accelerated from the polarregions of the protostar/disc interface intoopposite directions along the open stellarmagnetic field. This reconnection-driven jetis further accelerated magneto-centrifugallydue to stellar rotation and excavates theambient medium. Eventually, a bipolar high-velocity neutral wind forms an hourglass-like cavity which reflects light from the veryinner regions of the system. Further out thisneutral wind drives the observed molecularbipolar flow.

In more general terms, our data show forthe first time that massive star formation viaaccretion is a realistic scenario. Large accre-tion discs can obviously withstand the harshenvironment of a dense stellar cluster andare not disrupted by tidal forces. Likewise,the ionising radiation and the stellar windsof nearby massive stars do not disturb theaccretion process. As a by-product of ourresults it follows that the star formationprocess which started some million yearsago in M17 is still continuing and is current-ly producing a second generation of massivestars. Thus, it is likely that once star forma-tion has been started in a molecular cloud,the parent generation of stars triggers thecreation of a new generation.

AACKNOWLEDGEMENTSCKNOWLEDGEMENTSWe thank the directors of ESO and IRAM for theallocation of discretionary time to perform theadaptive optics image and the molecular lineobservations, respectively. We also thank theParanal Science Operations team which has per-formed the infrared observations in service mode.We thank M. Paegert for providing the drawingfor Figure 4. This work was supported by theNordrhein-Westfälische Akademie der Wissen-schaften.

RREFERENCESEFERENCESBonnell I., Bate M., Zinnecker H. 1998, MNRAS,

298, 93Calvet N. 1997, IAU Symposium 182, 417Chini R. et al., 2004, Nature, 429, 155Chini R., Wargau W. 1998, AA, 329, 161Hartmann L., Hewett R., Calvet N. 1994, ApJ,

426, 669Muzerolle J., Hartmann L., Calvet N. 1998, AJ,

116, 455Shu F., Adams F., Lizano S. 1987, ARA&A, 25,

23 Wolfire M., Cassinelli J.P. 1987, ApJ, 319, 850Yorke H., Sonnhalter C. 2002, ApJ, 569, 846

© ESO - September 2004 39Chini R. et al., The birth of a massive star

Figure 5: Schematic picture of the protostellar disc/outflow system. The individual com-ponents are drawn to scale with the suggested orientation to the observer; accretiondisc (black), hourglass shaped cavity (blue), bipolar precessing jet (yellow), elongatedcentral object (white).

The Messenger 11740

TTHE HAMBURG/ESO OBJECTIVE-prism survey (HES) was car-ried out with the ESO-Schmidttelescope from 1990 to 1998 inthe course of a Key Program-

me (No. 145.B-0009; P.I.: Reimers). Thefinal survey area consists of 380 fields cov-ering a nominal area of 9500 square degrees,i.e., the total southern extragalactic sky. Theplates have been digitized at HamburgerSternwarte, yielding a data base of almost 5million spectra of objects in the magnituderange 10 <~ B <~ 17.5. The driving aim of theHES during its constitution was the pursuitof a wide angle survey for the brightestquasars in the southern hemisphere (seeReimers 1990; Reimers & Wisotzki 1997).The digital database enabled us to efficient-ly select quasar candidates using variouscolour criteria supplemented by spectral fea-ture detection (Wisotzki et al. 2000). Quasarcandidates were followed up mostly by ESOtelescopes, which resulted in the measure-ment of over 2000 quasar redshifts, provid-ing by far the largest existing homogeneousset of bright quasars in the south. Besidesconstraining the bright end of the QSO lumi-nosity function, the survey yielded high-lights such as the discovery of several grav-itationally lensed quasars, and the firstdetection of the epoch of He II reionization.

It was realized right from the start thatthe spectral resolution of the objective-prismspectra would be sufficient for stellar surveywork as well. The spectral resolution is typ-ically 1 nm at Ca II K, depending on the see-ing conditions during the observations of theplates. The resolution of the spectra provedquite useful, at first, mainly to eliminate thestellar contamination of quasar candidatesamples. Notice that already a pure UVexcess selected sample in the magnituderange of the HES has more than 90% starsand less than 10% quasars. This ratio

increases further if the selection includesalso non-UV-excess objects. Yet, the strongBalmer lines of DA white dwarfs and FieldHorizontal-Branch A-type (FHB/A) stars areeasily detected already in the digital prism

spectra, but also e.g. the much weaker He Ilines of DB white dwarfs and hot subdwarfs,or the Ca II H and K lines of cool stars (seeFigs. 1 and 3). Recognizing these featureshelped enormously to achieve a hitherto

TTHEHE SSTELLARTELLAR CCONTENTONTENT OFOF THETHE

HHAMBURGAMBURG/ESO S/ESO SURURVEYVEYWE REPORT ON THE EXPLOITATION OF THE STELLAR CONTENT OF THE HAMBURG/ESO OBJECTIVE-PRISM

SURVEY (HES), WHICH COVERS THE TOTAL SOUTHERN EXTRAGALACTIC SKY DOWN TO B ≈ 17.5. QUANTITATIVE

CRITERIA HAVE BEEN DEVELOPED FOR SELECTING INTERESTING STARS IN THE DIGITAL HES DATABASE,CONTAINING ALMOST 5 MILLION SPECTRA. WE GIVE AN OVERVIEW OF ONGOING PROJECTS DIRECTED AT

FINDING EXTREMELY METAL-POOR STARS, FIELD-HORIZONTAL BRANCH A-TYPE STARS, CARBON STARS, AND

WHITE DWARFS. HIGHLIGHTS OF THESE EFFORTS ARE THE DISCOVERY OF MORE THAN 200 NEW EXTREMELY

METAL-POOR ([Fe/H] < –3.0) STARS, INCLUDING THE MOST METAL-POOR STAR KNOWN SO FAR, HE0107-5240([Fe/H] = –5.3), AND THE DISCOVERY OF MANY NEW MAGNETIC DA AND DB WHITE DWARFS AND OTHER PECU-LIAR WHITE DWARFS.

N. CN. CHRISTLIEBHRISTLIEB 11, D. R, D. REIMERSEIMERS 11, L. W, L. WISOTZKIISOTZKI 22

1HAMBURGER STERNWARTE, UNIVERSITY OF HAMBURG; 2ASTROPHYSIKALISCHES INSTITUT POTSDAM

Figure 1: Sample spectra of various stellar objects detected in the Hamburg/ESO survey. Note that wavelength is decreasing from left to right. The sharpdrop at about 5400 Å is due to the sensitivity cutoff of the photographic emul-sion (IIIa-J) of the HES objective-prism plates.

unparalleled (for an optical quasar survey)follow-up efficiency of ~70%, without anycompromises in completeness (Wisotzki etal. 2000). However, one person’s leftoversmay become another person’s wealth, in thiscase a wealth of interesting stars. It wasdecided that there was so much potentialinformation in this survey for studies of thestellar populations of the Milky Way that adedicated effort was certainly desirable, andwe developed quantitative methods for theselection of interesting stellar objects in theHES. We started by exploring techniques ofautomatic spectral classification applied tothe entire digital HES data base (Christliebet al. 2002). Our work subsequently focusedon searching for specific types of rare starswith efficient selection techniques.

Here we describe some of the most suc-cessful projects that emerged: selection ofmetal-poor stars, carbon stars, FHB/A stars,and white dwarfs. Other projects which wedo not discuss here are searches for T Tauristars, subdwarf B and O stars, and cata-clysmic variable stars.

SSTELLARTELLAR AARCHAEOLOGYRCHAEOLOGY ANDANDNNEAREAR--FIELDFIELD CCOSMOLOGYOSMOLOGY WITHWITH

MMETETALAL--POORPOOR SSTTARSARSMetal-poor stars preserve in their atmos-pheres, to a large extent, the chemical com-position of the gas clouds from which theyformed. They can hence be used for “stellararchaeology”: their abundance patterns pro-vide information on the first, now extinctgeneration of massive stars which endedtheir lives in supernova type-II (SN II)explosions. In particular, the most metal-poor stars constrain the yields of these SN IIof Population III stars (i.e., stars with thechemical composition of Big Bang materi-al), and the mass-distribution of the firstgeneration of stars. They also allow one todetermine the nature and constrain the sitesof nucleosynthesis processes such as theslow (s) and rapid (r) neutron-captureprocesses in the early Universe. There arealso cosmological applications of metal-poor stars. Their ages provide an independ-ent lower limit for the age of the Universe.Metal-poor stars with strong enrichment ofelements produced in the r-process providethe opportunity to determine individual stel-lar ages using long-lived radioactive iso-topes, such as 232Th (half-life 14.05Gyr) or238U (4.468Gyr). By comparing the abun-dance ratio of one of these elements relativeto a stable r-process element (e.g., Th/Eu orU/Eu) to the production ratio expected fromtheoretical r-process yields, the time elapsedsince the nucleosynthesis event that pro-duced these elements took place can bederived. Alternatively, U/Th can also beused as a “cosmo-chronometer” (Cayrel etal. 2001).

The convection zones of unevolved starsnear the main-sequence turnoff are shallow

enough to prevent lithium from beingdestroyed in deeper, hotter layers of the star.Therefore, it is thought that the Li abun-dances in the atmospheres of old, metal-poorturnoff stars reflect the Li abundance pro-duced in Big Bang nucleosynthesis (BBN).Using BBN models, the baryon density ofthe Universe can be derived from the “Spiteplateau” value of the Li abundance.However, a recent investigation based on 23metal-poor stars in the range1 –3.6 <[Fe/H] < –2.3 has shown that the Spiteplateau is actually not a plateau but exhibitsa trend with [Fe/H]. The scatter around thistrend is very small (i.e., σ < 0.031 dex) andfully accountable by measurement errors,not an intrinsic scatter (Ryan et al. 1999).The Li trend can be explained by galacticchemical evolution (i.e., Li might have beenproduced e.g. by Galactic cosmic-ray spalla-tion). A larger sample of metal-poor turnoffstars extending to lower [Fe/H] would helpto pin down the steepness of the Li trendmore accurately and reduce the extrapola-tion to the primordial Li abundance.

The above reasons justify the investmentof considerable amounts of telescope time

(in addition to the survey itself) in findingmore metal-poor stars and studying largesamples of them in detail. In the HES, onlycandidates for metal-poor stars can beselected. These have to be confirmed bymoderate-resolution follow-up spectroscopybefore they can enter target lists for high-resolution spectroscopy (see Fig. 2 for sam-ple spectra from these observational steps).

SSELECTIONELECTION OFOF

METMETALAL--POORPOOR CANDIDACANDIDATESTES

A total of ~10,000 metal-poor candidates hasbeen selected in the HES. Stars with a Ca IIK line which is weaker than expected for astar with [Fe/H] = –2.5 at a given B–V colourare selected as candidates. B–V can be meas-ured with an accuracy of 0.1mag from theHES objective-prism spectra (Christlieb etal. 2001a) and is therefore available for allHES stars. Figure 3 illustrates the selectionprocedure with three bright stars of similartemperature from the HK survey of Beersand collaborators (Beers et al. 1992) whichhave been rediscovered in the HES. One canclearly see the decreasing strength of Ca II Kwith decreasing [Fe/H].

© ESO - September 2004 411[X/H] = log10 [N(X)/N(H)]& – log10 [N(X)/N(H)]A , and analogously for [X/Fe].

Figure 2: Thethree observationalsteps leading toabundances ofmetal-poor stars.About 10,000 can-didates are select-ed in the HES (step1). These are spec-troscopically fol-lowed up (step 2),yielding confirmedmetal-poor starswhich are thenobserved at highspectral resolution(step 3) with 8m-class telescopes.

It is impossible to follow-up thousandsof metal-poor candidates in single-slit modeat a single observatory, because typicallyonly 20–40 stars can be observed in a clearnight. Therefore we employ a variety offacilities in both hemispheres for this task.2

About half of the metal-poor candidateshave been observed so far, and more than200 stars have been confirmed to have[Fe/H] < –3.0. This trebles the total numberof known stars in this metallicity regimefrom previously ~100 to now more than 300.In Fig. 4 we compare the metallicity distri-bution function (MDF) of a representativesubset of the observed HES candidates withthe MDF of the HK survey candidates. It canbe seen that the fraction of stars at[Fe/H] > –2.0 is considerably lower in theHES, i.e., the candidate selection efficiencyis much higher. While in the HK survey only11% and 1% of the candidates are genuinelybelow [Fe/H] = –2.0 and [Fe/H] = –3.0,respectively, the efficiency for stars havingunsaturated spectra in the HES is about afactor of five higher (Christlieb 2003). Forthe 1767 (partly) saturated HES stars in themagnitude range 10 <~ B <~ 14, the efficiencyis still a factor of two higher than in the HKsurvey (Frebel et al., in preparation). Thereasons are the higher quality of the HESspectra and the employment of an automatedand quantitative selection as opposed tovisual inspection of objective-prism platesusing a binocular microscope.

High-resolution spectra of the confirmedmetal-poor stars are being obtained withVLT/UVES, Keck/HIRES, Subaru/HDS andMagellan/MIKE. In the next two sectionswe present selected highlights from theseefforts.

HE0107-5240HE0107-5240For more than 20 years, it has been assumedthat there is a low-metallicity “cutoff” in themetallicity distribution function of the galac-tic halo, at [Fe/H] ~ –4.0, i.e., 1/10,000 ofthe metallicity of the Sun (see Fig. 4). Twoof the physical reasons that have been sug-gested to explain the absence of stars with[Fe/H] < –4.0 are pre-enrichment of theinterstellar medium by supernovae of type IIto [Fe/H] > –4.0, or suppression of low-massstar formation due to the absence of coolingmechanisms in ultra metal-poor gas clouds(see e.g. Bond 1981).

Hence it was rather surprising to discov-er HE0107-5240, a giant with [Fe/H] = –5.3(Christlieb et al. 2002; see also ESO PressRelease 19/02). This star was found duringspectroscopic follow-up observations at theSiding Spring Observatory 2.3m. High-reso-lution spectra were obtained with VLT/UVES in 2001 and 2002. The elements

The Messenger 11742

Figure 4: Metallicity distribution function of metal-poor candidates selected in the HK (upperpanels) and HE (lower panels) surveys. Note the much smaller fraction of stars with[Fe/H] > –2.0 in the HES.

Figure 3: HESsample spectra ofmetal-poor stars.An enlargement ofthe spectral regioncovering Ca II H +Hε and Ca II K isshown in the upperright corner of eachpanel. The 1-σnoise level of eachpixel of the digitalobjective-prismspectra is overplot-ted. In the spec-trum of the bright(B = 14.9) starCS30339-69 =HE0027-3613, theCa K line is barelydetected eventhough the star hasa metallicity as lowas [Fe/H] = –3.2.

2This includes the ESO 3.6m/EFOSC2, SSO2.3m/DBS, UK 1m-Schmidt/6dF, Magellan 6.5m/B&C,Palomar 200)/DS, CTIO and KPNO 4m/RCSPEC, andthe 4m Anglo-Australian Telescope/RGO.

heavier than Na are depleted by amountssimilar to that seen for Fe, while carbon andnitrogen are strongly enhanced with respectto iron and the Sun, by 3.7–4.0 and2.3–2.6 dex, respectively. Na is also strong-ly enhanced ([Na/Fe] = +0.8 dex).

A lot of the discussion in the recent liter-ature has focused on explaining the origin ofthe abundance pattern of HE0107-5240.Particularly interesting is the supernovamodel of Umeda & Nomoto (2003) of aPopulation III star of about 25 solar massesthat explodes with low explosion energy(Eexp = 3 · 1050 erg) followed by mixing andfallback. It produces elemental yields that fitthe overall abundance pattern of HE0107-5240 rather well, in particular the high C toN and light to heavy element ratios.However, the oxygen abundance predictedfor HE0107-5240 is [O/Fe] = 3.0 dex, whileBessell et al. (2004) measure [O/Fe] =2.3+0.2

–0.4 dex. It remains to be studied whetherthis disagreement can be reduced by modify-ing one of the free parameters of the Umeda& Nomoto model, e.g., the progenitor mass,and/or the mass coordinate range in whichmixing occurs. One advantage of theUmeda & Nomoto pre-enrichment scenariois that it might solve the “star formationproblem”. While it is difficult to form a 0.8solar mass star from a gas cloud with[Fe/H] = –5.3, the presence of a lot of carbonand oxygen would provide efficient coolingchannels (Umeda & Nomoto 2003; Bromm& Loeb 2003).

It has also been argued that HE0107-5240 might even be a Population III star, i.e.,a star originally consisting only of materialproduced in the Big Bang. The abundancesof most heavy elements observed inHE0107-5240 are so low, and the age of thestar presumably so large (on the order of theage of the Universe), that its abundancesmight have been severely changed by accre-tion from the interstellar medium (Christliebet al. 2002; Shigeyama et al. 2003). Thelarge amount of carbon, nitrogen and oxygenmight have been accreted from a formerlymore massive companion which is now awhite dwarf (Christlieb et al. 2002; Suda etal. 2004). However, if it is assumed thatthere was no pre-enrichment of the gas cloudfrom which HE0107-5240 formed, it isunclear how the star could have formed.

Based on new calculations of the evolu-tion of and nucleosynthesis in ultra metal-poor low-mass stars, two groups arguedindependently that self-enrichment ofHE0107-5240 with CNO can be excluded(see Weiss et al. 2004, and references there-in), because the predicted abundances of Cand N are too large by several orders of mag-nitude; the predicted C/N ratio is close to 1,while 50 is observed; and the predicted12C/13C isotopic ratios are about a factor often lower than the lower limit of 50 observedin HE0107-5240.

In summary, HE0107-5240 gives us theopportunity to learn about star formationprocesses in the early Universe, the first gen-eration of stars exploding as supernovae,and stellar evolution at extremely-lowmetallicities. Therefore, its discovery hassparked a lot of new research. Some of theelements that we see in HE0107-5240 mightbe associated with the very first nucleosyn-thesis events in the Universe, occurring inthe stars that formed only about 200 Myrafter the Big Bang, according to recentresults obtained with the WilkinsonMicrowave Anisotropy Probe.

R-R-PROCESSPROCESS ENHANCEDENHANCED STSTARSARS

We have started a dedicated effort to findmore stars with strong enhancements (i.e.,by more than a factor of 10) of neutron-cap-ture elements associated with the r-process.In the course of a Large Programme (No.170.D-0010; P.I.: Christlieb), “snapshot”spectra of 373 confirmed metal-poor giantsbrighter than B ~ 16.5 mag, including 4comparison stars, are scheduled to beobtained with VLT/UVES. Most of the tar-gets are from the HES. The snapshot spectratypically have R = 20,000 and S/N = 30,which is sufficient for measuring the abun-dances of some 20 elements and recognizingr-process enhanced and other interestingstars. The snapshot spectra are being securedwhen the seeing at Paranal is > 1.2), and theconstraints on the other observing conditionsare very low. This “filler program” philoso-phy has already been employed successfullyin the SPY project (Napiwotzki et al. 2003)aiming at finding supernova type Ia (SN Ia)progenitors (see also below).

So far we have received and analyzedsnapshot spectra of 350 stars. We have found10 new stars with enhancements of r-processelements by more than a factor of 10, astraced by Eu (i.e., [Eu/Fe] > 1 dex). That is,we have increased the number of knownstars of this kind by more than a factor of 4,from previously 3 (CS22892-052, CS31082-001, and CS22183-031) to now 13. High-quality spectra of at least 5 of the new starswill be obtained in the course of the LargeProgramme.

The first new strongly r-processenhanced star that we discovered, CS29497-004, shows an enhancement of Ba to Dy byon average 1.5 dex with respect to iron andthe Sun (Christlieb et al. 2004). The abun-dances of the elements with Z ≥ 56 match ascaled solar r-process pattern well, while This underabundant relative to that pattern by0.3 dex, which we attribute to radioactivedecay. The CH features in the spectrum ofthis star are much weaker than in CS22892-052 and about as weak as in CS31082-001,making it a good candidate for an attempt todetect uranium. VLT/UVES spectra of suffi-cient quality for this enterprise have alreadybeen obtained and are currently being ana-

lyzed. As a by-product of the Christlieb etal. Large Programme, we have almost dou-bled the number of stars confirmed by high-resolution spectroscopy to have [Fe/H] <–3.5, from 8 to 15. Furthermore, we haveassembled by far the largest homogeneouslyanalyzed sample of extremely metal-poorstars to date. This allows us to examine theabundance trends and scatter around thesetrends for this large sample, which is ofunprecedented value for investigations ofgalactic chemical evolution.

The homogeneous analysis of 350 starswas feasible because an automated abun-dance analysis technique (Barklem et al.2004) has been used. It has been specificallydeveloped for our Large Programme, but itis general in the sense that it can be appliedto high-resolution spectra of other stars aswell (e.g., more metal-rich stars) if appropri-ate line lists are compiled.

CCARBONARBON SSTTARSARSChristlieb et al. (2001b) identified 403 fainthigh latitude carbon (FHLC) stars in theHES by means of their strong C2 and CNfeatures (see upper right panel of Figure 1for an HES example spectrum). Spectro-scopic follow-up observations have revealedthat this sample consists of a mixture ofintermediate-mass asymptotic giant branch(AGB) stars and earlier type, metal-poor, butcarbon-rich stars. Already from the HK sur-vey it was apparent that about 20% of themetal-poor stars at [Fe/H] < –2.5 havestrong overabundances of carbon, i.e.,[C/Fe] > 1.0. This is confirmed by the HES,with the most extreme case found so farbeing HE0107-5240. A selection of starswith strong carbon features therefore pro-vides an independent means for selecting themost metal-poor stars.

The carbon-enhanced metal-poor starsthat show enrichment with s-process ele-ments give us observational access to anextinct generation of extremely metal-poorAGB stars that via mass transfer left their“fingerprints” on their less massive compan-ions, which we observe today. They providestrong observational constraints for simula-tions of the structure, evolution and nucle-osynthesis of AGB stars, and allow us toinvestigate the s-process at very low metal-licities. One extreme case which was foundin the HES is HE0024-2523. Lucatello et al.(2003) analyzed high-resolution spectraobtained with Keck/HIRES as well asVLT/UVES, and find that it is a short-period(P = 3.4126 days) binary with a very largeoverabundance of the s-process elements;e.g., [Ba/Fe] = 1.5, and [Pb/Fe] = +3.3. Thehigh overabundances of Pb in this and other“lead stars” are in concert with theoreticalcalculations, which predict that an efficientproduction of s-process elements takes placeeven in very low metallicity AGB starsdespite the shortage of iron seeds, provided

© ESO - September 2004 43Christlieb et al., The Stellar Content of the Hamburg/ESO Survey

that protons are mixed into carbon-rich lay-ers. Proton mixing results in formation of13C, which is a strong neutron source due tothe reaction 13C(α, n)16O.

It is likely that there are more “leadstars” among the 403 HES FHLC stars ofChristlieb et al. (2001b). High-resolutionspectra of many good candidates and addi-tional stars from the metal-poor star samplehave already been obtained withVLT/UVES.

Among the original motivations forselecting FHLC stars in the HES was also tocompile a large, homogeneously selectedsample of dwarf carbon stars (dCs), i.e.,main-sequence stars with strong overabun-dances of carbon – not to be confused withDQs, i.e., white dwarfs with strong carbonfeatures in their spectra (see upper left panelof Figure 1 for an example). However, theseefforts have now been superseded by the(much deeper) Sloan Digital Sky Survey(SDSS), in which so far more than 100 dCshave been found, and a total of 200-300 areexpected to be detected in the full survey.

FFIELDIELD-H-HORIZONTORIZONTALALBBRANCHRANCH A-A-TYPETYPE SSTTARSARS

Field horizontal branch A-Type (FHB/A)stars are valuable tracers for the structureand kinematics of the halo of the Galaxy. Inthe HES, FHB/A stars with distances of upto ~ 30 kpc can be found. Another applica-tion of FHB/A stars is distance estimation ofHigh Velocity Clouds (HVCs). HVCs areclouds of neutral hydrogen having radialvelocities incompatible with Galactic differ-

ential rotation. There is an ongoing discus-sion as to whether HVCs are Galacticobjects, or if they are extragalactic.Distances to HVCs can be determined byusing stars of known distance in the line ofsight of the clouds. Provided that the HVCunder consideration has a detectable metalcontent, we see absorption lines of thesemetals at the velocity of the cloud in thespectra of stars located behind the cloud, butdo not see these lines in spectra of starslocated in front of the cloud. By using sever-al stars at different distances in the line ofsight of the cloud we can constrain its dis-tance. FHB stars are particularly well-suitedfor this purpose, because they are numerous,distant, and their spectra are almost free ofintrinsic absorption lines of metals.

Using the techniques of automatic spec-tral classification of Christlieb et al. (2002),we have identified 8321 FHB/A candidatesin the HES. Representative follow-up obser-vations of ~200 stars with the 3.6m/EFOSC2as well as the CTIO and KPNO 4m tele-scopes have shown that the contamination ofthe sample with the less distant “blue metal-poor stars” of Preston et al. (the majority ofwhich are likely halo blue stragglers) is lessthan 10%, while it would be as high as 1/3 inpurely flux-limited sample of field A-typestars at high galactic latitudes. The contami-nation could be kept low by using theStrömgren c1 index, which can be directlymeasured in the HES spectra with an accura-cy of 0.15 mag (Christlieb et al. 2001a), as agravity indicator. The stars are being used asHVC distance probes in ongoing observa-tional programs at ESO and elsewhere.

WWHITEHITE DWDWARFSARFS ANDAND OTHEROTHER““FFAINTAINT BLUEBLUE STSTARSARS””

White dwarfs (WDs) are a common by-product of any QSO survey since bluecolour selection will detect WDs withT >~ 10,000 K. At the HE survey limit ofB <~ 17.5 for the stellar work, typically twoDA WDs per Schmidt plate can be selectedunambiguously. The advantage of the HEcompared to the PG survey, a UV excessQSO survey, is that blue subdwarfs, whichdominate the population at 16 mag, can bereliably separated from QSOs and WDsspectroscopically at the spectral resolutionof the HES. The DA search yielded 830 DAcandidates, 737 of them are not listed in thecatalogue of McCook & Sion (1999).Christlieb et al. (2001a) estimate that thecontamination of this sample with non-WDsis less than 10%.

The high and uniform density of brightWDs over the whole southern sky providedby the HES was a pre-requisite of the SPYproject, a search for SNIa progenitorsamong double degenerates (DDs) conductedas a Large Programme with UT2/UVES(Napiwotzki et al. 2003). In addition to theDA search, an automated DB search hasbeen conducted for SPY as well (Christliebet al., in preparation). Besides the dedicatedsearch for WDs, the follow-up spectroscopyof QSO candidates yielded a number ofmore peculiar WDs not recognizable direct-ly on the Schmidt plates, e.g., WDs withextremely high magnetic field strengths andextremely hot new types of WDs. In the fol-lowing we highlight the most important newHE faint blue stars. Table 1 lists these high-lights.

MMAGNETICAGNETIC WDWDSS

The discovery of HE1211-1707 andHE1043-0502 (Reimers et al. 1996, 1998)together with dedicated calculation of theHe I spectrum in fields up to 1000 MG (e.g.Becken 2001) which were motivated also bythese discoveries, led to an improved (first)understanding of He I in strong magneticfields. HE1211-1707 is an ideal test objectsince it is a highly spectrum variable DBwhite dwarf with a mean field of 50 MG(Wickramasinghe et al. 2002) and a periodof 110 min (Jordan 2001). An even moreexotic case is HE1043-0502: it shows anextremely strong feature near 445.0nm(Reimers & Wisotzki 1997; see also Fig. 1).According to Wickramasinghe et al. (2002)these features can be explained on the basisof Beckens and Schmelchers (2001) quan-tum mechanical calculation of He I in strongmagnetic fields as 21S0–31P0 transition at800 MG. Since the 445.0nm feature is a“stationary component” one would expectmore objects of the HE1043-0502 type.However, our dedicated search in the HESdata base, using the spectrum of HE1043-0502 as a template, and follow-up spec-

The Messenger 11744

Table 1: Remarkable “faint blue stars” from the HES

Name Name TType ype

HE0015+0024 magn. DB with Zeeman triplets; B = 6MG (Figure 5)HE1043-0502 magnetic DB, B ~ 800MGHE1211-1707 variable magn. DB, B = 50MG, P = 110 minutes HE0330-0002 non-DA magn. WD, unidentified lines HE0236-2656 non-DA magn. WD, unidentified lines HE0241-0155 magn. DA, B = 150-400 MG, Grw +70° 8247 type HE1045-0908 magn. DA, P = 2-4 hours, B = 30 MG [20 MG?; Schmidt et al.]HE0504-2408 DO with ultrahighly excited lines HE1314+0018 DO with unexplained strong He II lines

HE1414-0848 double degenerate, M1 + M2 = 1.26 MA

HE2209-1444 double degenerate, M1 + M2 = 1.15 MA

HE0301-3039 first sdB + sdB binary

HE1146-0109 DQ with exceptionally strong C2 and CI lines HE0127-3110 variable He I spectrum, transient C2 bands,

variable high velocity components, AM CVn type?

troscopy of candidates at the 3.6m telescopewas not successful. Instead, a number ofhighly peculiar broad-absortpion linequasars with a feature at 445.0nm and manynew DBs were discovered. In conclusion,DB white dwarfs with field strengths as highas 800 MG appear to be extremely rare.

Among the newly-discovered magneticDAs, two are especially noteworthy:HE1045-0908 and HE0241-0155. The for-mer shows a distinctive, rich Zeeman spec-trum. Schmidt et al. (2001) discovered spec-trum and circular polarization variabilityover one hour. The period is not yet precise-ly known, but should be in the range 2–4hours. Observing and modeling this starmight yield new information on departuresfrom simple dipole configuration (seeSchmidt et al. 2001).

HE0241-0155, with a magnetic field of150–400 MG, is similar to the prototype ofstrong field DAs, Grw +70° 8247. On theother hand it shows features in the spectrumbetween 500 and 550nm which cannot beexplained by the normal stationary compo-nents that require a large homogeneous fieldwith 200 MG field strength, possibly due toa large spot. One might expect variabilitydue to the spot. However, a new spectrumtaken 5 years later (2003) does not revealany variations.

NNEWEW DO DO TYPESTYPES

Werner et al. (1995, 2004) have discoveredtwo new types of extremely hot WDs amongthe HE follow-up spectra. HE0504-2408 isone of the prototypes of DO white dwarfswith lines from ultra-high ionization stateslike Ne IX or O VIII. HE1314+0018 is aDO with exceptionally strong He II absorp-tion lines. Both phenomena are not explain-able within the concept of static non-localthermodynamic equilibrium stellar atmos-pheres. They possibly originate in expand-ing coronae/winds of hot WDs. The strongHe II lines could also be due to an unusualcomposition of the atmospheres notdetectable in the optical spectral range.

SPY – TSPY – THEHE SEARCHSEARCH FORFOR

SNISNIAA PROGENITORSPROGENITORS

This ESO Large Program has been describedin detail by Napiwotzki in the Messenger(Napiwotzki et al. 2003). In recent yearsSNIa have played an increasing role as dis-tance indicators in cosmology up to redshiftsof more than 1 and they have provided evi-dence for a non-vanishing cosmologicalconstant, independent of other measure-ments like microwave background fluctua-tions. However, since the progenitors ofSNIa are not known there remains room forspeculations on intrinsic variations of SNIapeak luminosities with cosmic epoch. Oneof the progenitor scenarios is the doubledegenerate (DD) scenario where two WDswith total mass above the Chandrasekharlimit (1.4 solar masses) merge within aHubble time due to angular momentum lossvia gravitational radiation. SPY aimed atdetecting DD systems by repeated spec-troscopy of about 1000 WDs, including DAsas well as non-DAs. More than 100 DDshave been discovered, 16 with double lines.Two systems (HE1414-0848, HE2209-3039) qualify nearly for SNIa progenitors, athird one appears to make it (Napiwotzki et

al., in preparation). SPY has demonstratedthat the DD scenario is one of the possibleevolutionary paths leading to a SNIa. Thelarge population of newly discovered DDswill allow us to study more quantitativelythe pre-SNIa stages, e.g. the common enve-lope phase which is difficult to model fromfirst principles.

HE0127-3110HE0127-3110AA NEVERNEVER ENDINGENDING STORSTORYY??

Three spectra of HE0127-3110 taken inSeptember and December 1994 show broadabsorption features at 465.0nm and 505.0nmand a relatively narrow line at 587.0nm.These spectra have been reproduced suc-cessfully by a magnetic DA model with fieldstrengths between 85 MG and 235 MG, inparticular the 587.0nm feature appeared tobe the well-known stationary 2S0→

3P0 Hαcomponent (Reimers et al., 1996). It wasalso discussed in the discovery paper that thebroad features might be the C2 Swan bands,and that the 587.0nm is He I 587.6nm, whileHe I 447.1nm was missing. However, thispossibility was dismissed because no singleWD model can explain the simultaneousoccurrence of strong C2 and He I.

Later, we discovered that we had taken aspectrum of HE0127-3110 already inSeptember 1992, which looked like a pureDB spectrum with both He I 447.1 and587.6nm but without the “C2 features”(Friedrich et al. 2000). The magnetic DAhypothesis was wrong. This conclusion wasindependently also reached by Schmidt et al.(2001), who found that HE0127-3110 doesnot show any circular polarization.

Was the C2 band due to a cool spot onthe DB which would re-appear one day byrotation? We have taken more than a dozenspectra between 1998 and 2003 with thehope to see again the C2 bands, but withoutsuccess (see Fig. 6). However, the He I587.6nm and 447.1nm lines appear to varyon the timescale of days, in particular He I447.1nm is weak or absent in several spec-

© ESO - September 2004 45Christlieb et al., The Stellar Content of the Hamburg/ESO Survey

Figure 5: 3.6m/EFOSC2 spectrum of the magnetic DB white dwarfHE0015+0024, clearly showing Zeeman triplets of He I 4471 and He I 5876.

Figure 6: Slitspectra of thespectrum vari-able objectHE0127-3110.

tra. Two UVES spectra of HE0127-3110taken in the course of the SPY project with-in 3 days give a hint to a possible solution ofthe problem. The He I 587.6 nm line is verybroad and shallow (line depth 20 %) and hasa narrow, deeper satellite component at+1330 km/s relative to the broad He I587.6 nm line (see Fig. 7). The narrow com-ponent moved to +1260 km/s within 3 days.Velocities that high and variable on shorttimescales in the context of an otherwisemostly “normal” DB spectrum hint to aclose double degenerate (DD), possibly ofthe AM CVn type, i.e., binaries in contact,with periods as short as 15 minutes. Andwhat about the C2 features? Could they havebeen produced as transient features in anoutburst which ejected carbon? We invite theinterested CV community to take the nextobvious steps: photometry and spectroscopywith high time resolution (minutes) andpolarimetry – not easy for a B = 16 mag star.

OOUTLOOKUTLOOKDue to technical reasons, so far only 329 ofthe 380 HES plates have been used for theexploitation of the stellar content of the sur-vey. Given the tremendous success of thiseffort, we are now in the process of extend-ing it to the remaining 51 plates.

We also plan to continue with collectingmedium-resolution follow-up spectroscopyfor at least the most interesting of theremaining ~5000 HES candidates for metal-poor stars. The ESO 3.6m with its very effi-cient instrument EFOSC2 is the ideal tele-scope/instrument combination at ESO forsuch an effort, which emphasizes the contin-ued need for “small” telescopes even in theera of 8-10m class telescopes.

In addition to the more than 200 newstars with [Fe/H] < –3.0, we have also founda few more stars which appear from themoderate-resolution spectra to have

[Fe/H] < –4.0. Some of them might turn outto have metallicities even much lower,because the Ca II K line, which is used forestimating [Fe/H] from the follow-up spec-tra, might be contaminated by CH lines(which is the case in HE0107-5240), inter-stellar absorption, or the Fe abundancemight be overestimated due to the presenceof a strong over-abundance of the α-elementCa. This can only be clarified by high-reso-lution spectroscopy. HE0107-5240 wasfound in a set of ~2000 of the best metal-poor candidates (which in turn have beenselected from about 1 million objects). Sincethe total number of HES candidates is about10,000, it is not excluded that a few morestars with [Fe/H] < –5.0 might be found inthe HES. For the determination of the pri-mordial Li abundance it is most desirable tofind a turnoff star at this metallicity.

For all stars estimated to have[Fe/H] < –3.5 from the follow-up spectra,high-resolution spectroscopy is beingobtained in ongoing observing programs at8-10m-class telescopes. We plan to use theVLT for this in the future as well. Very highS/N is needed because the lines of elementsother than hydrogen are exceedingly weak atthe lowest metallicities.

Finding more metal-poor stars with[Fe/H] < –5.0 and significant numbers ofother interesting stellar objects wouldrequire us to extend the survey volume sig-nificantly with respect to the HES; that is, ithas to be much deeper. Such a survey is onlyfeasible if either the candidate selection effi-ciency is further improved, to reduce thenumber of candidates to be followed up insingle-slit mode, or if a large amount of timeat a suitable telescope with a multi-fiberspectrograph is available. Only in this waycan one cope with the large number ofmetal-poor candidates which would resulte.g. from a deeper colorimetric survey.

AACKNOWLEDGEMENTSCKNOWLEDGEMENTS

We thank T.C. Beers for helpful commentsand careful proof-reading. N.C. is grateful tohis numerous collaborators who have con-tributed over many years in various ways tomake the exploitation of the stellar contentof the HES a success. In the context of theresults described here, he would especiallylike to thank P.S. Barklem, T.C. Beers, M.S.Bessell, J. Cohen, A. Frebel, B. Gustafsson,V. Hill, D. Koester, S. Lucatello, and C.Thom. This work is supported by DeutscheForschungs-gemeinschaft, and a HenryChretien International Research Grantadministered by the American AstronomicalSociety. It has been supported by theEuropean Commission through a MarieCurie Fellowship and by the AustralianResearch Council through a Linkage Inter-national Fellowship, both awarded to N.C.

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The Messenger 11746

Figure 7: VLT/UVES spectra of He I 5876 in HE0127-3110. Note the sharp, movingcomponent at a radial velocity of ~1300 km/s relative to He I 5876.


TTHE MULTI-OBJECT SPECTROGRAPH

FLAMES is one of the mostrecent and valuable additionsto the instrument family of theESO Very Large Telescopes.

Its technical characteristics (see Pasquini etal. 2002 for details) make it the ideal istru-ment for medium-high resolution spectro-scopic studies of large numbers of stars inrelatively wide fields, reaching much faintermagnitude limits than previously possiblewith good accuracy. Galactic globular clus-ters (GC) are typical places where these con-ditions are met, and therefore are excellenttargets for FLAMES.

The scope of this article is to highlightthe results we obtained with the firstFLAMES observations, taken duringScience Verification (SV) in January-February 2003, on the GC NGC 2808. Thisis a very interesting and puzzling cluster(e.g. second-parameter bimodal horizontalbranch [HB] morphology, possible connec-tion with the recently discovered CMa dwarfgalaxy), yet no detailed spectroscopic studyof its RGB stars was available so far. Theprimary aim of these observations was to fillin this gap, with two scientific purposes inmind: i) investigate the mass loss phenome-non by detecting evidence of mass motionsin the atmosphere of these stars; and ii)derive the abundance of some key elements(e.g. sodium and oxygen) to study the chem-ical (in)-homogeneity along the RGB.

One of the basic requirements of stellarevolution theory is that some amount ofmass (~ 0.1-0.2 M0) must be lost by GCstars during the RGB evolutionary phase, inorder to explain the morphology of the sub-sequent HB evolutionary phase (cf. Renzini& Fusi Pecci 1988). However, very littleobservational evidence has been found so fareither of the mass already lost, or of the massloss phenomenon while it is happening.Several spectroscopic surveys have beencarried out for this purpose during the pastthree decades, but no firm conclusion could

be reached mainly because of lack of ade-quate data. The mass loss is likely a stochas-tic phenomenon, and accurate high resolu-tion spectra of a large number of faint starsare needed in order to gather the statisticalsignificance that is required for a correctunderstanding.

The indicators traditionally used to tracemass motions in the atmospheres (hencepossibly mass loss) are the Ca II K, Na I Dand Hα lines, through the analysis of profileasymmetries (e.g. Ha and Ca II K emission

wings) and core (blue) shifts. Other, perhapsbetter, indicators exist in the UV and IRranges (e.g. Mg II at 280nm, Lyα, He I at1083nm, cf. Dupree 1986), but are inacces-sible for such faint stars with availableequipment. Therefore, we have observedthese three visual lines in 137 RGB starswith GIRAFFE in MEDUSA mode(R=19,000–29,000), monitoring ~3 magdown from the RGB tip. Of these stars, 20were observed in UVES mode to get theNa I D and Hα lines at higher resolution

FLAMES FLAMES SSPECTROSCOPYPECTROSCOPY OFOF RGB RGB STSTARSARS

ININ THETHE GGLOBULARLOBULAR CCLUSTERLUSTER NGC 2808: NGC 2808: MMASSASS LLOSSOSS ANDAND NNAA-O -O AABUNDANCESBUNDANCES

A SPECTROSCOPIC SURVEY WITH FLAMES OF 137 RED GIANT STARS IN THE GLOBULAR CLUSTER NGC 2808HAS REVEALED THE LIKELY PRESENCE OF MASS LOSS IN A LARGE NUMBER OF STARS AMONG THE BRIGHTEST

SAMPLE. CHEMICAL INHOMOGENEITIES ALL ALONG THE 3-MAG MONITORED INTERVAL SUGGEST PRIMORDIAL

POLLUTION FROM A PREVIOUS GENERATION OF INTERMEDIATE MASS STARS.

C. CC. CACCIARIACCIARI , A. B, A. BRAGAGLIARAGAGLIA, E. C, E. CARRETTARRETTAA

INAF, OSSERVATORIO ASTRONOMICO DI BOLOGNA, ITALY

Figure 1: Colour-Magnitude diagram of NGC 2808 (Bedin et al.2000) showing the 137 RGB stars observed with FLAMES. Filled redcircles indicate the stars observed with UVES, circled blue dots indi-cate the stars observed with GIRAFFE/MEDUSA.

(R=47,000). The location in the Colour-Magnitude diagram of these 137 RGB starsin shown in Figure 1. The results of thisstudy, as well as a detailed discussion andreferences to previous studies, have beenpresented by Cacciari et al. (2003) and arehere summarized.

We show in Fig. 2 the Hα lines after sub-traction of a template observed profile andof a theoretical profile, for the 13 starsobserved with UVES and brighter thanV=14.0 (logL/L0=2.88). They all show clearevidence of emission wings. Consideringalso the GIRAFFE spectra, we found that~95% of the stars brighter than this value doshow Hα emission wings. This is a muchlarger fraction than detected by any previousanalysis. The nature of this emission is notassessed definitely, as it may be present ineither stationary or moving chromospheres.However, blue-shifted Hα absorption coreswere detected in 7 out of the 20 UVES stars,and these are indicative of outward motionin the layer of the atmosphere where the Hαline is formed. Similarly, we found negativecoreshifts of the Na I D2 line in about 73%of the stars brighter than logL/L0~2.9. TheCa II K line was observed in 83 stars, 22 ofwhich show the central emission K2 andreversal absorption K3 features, with adetection threshold for these features atlogL/L0~2.6. Asymmetry B/R (i.e. theintensity ratio of the blue [K2b] and red [K2r]emission components) could be detected inabout 75% of stars brighter thanlogL/L0~2.9, and is mostly red (B/R<1)indicating outward motion. Velocity shifts ofthe K3 reversal relative to the photosphericlines have been measured, and are mostlynegative indicating that there is an outflowof material in the region of formation of theK3 core reversal. The onset of negative K3coreshifts occurs at logL/L0~2.8, i.e. at aslightly lower luminosity level than theonset of red asymmetry, and applies to near-ly 90% of the stars brighter than this value.This set of observational evidence confirmsthat mass loss may indeed be present alongthe RGB, especially in the brightest ~0.8mag interval from the RGB tip, and in a larg-er number of stars than previously estimatedwithin any given GC.

These same data were used to derivesodium abundances (for 81 of the starsobserved with GIRAFFE), and sodium plusoxygen abundances (for the 20 starsobserved with UVES). The results have beenpublished by Carretta et al. (2003, 2004),and are briefly summarized here.

The astrophysical scenario that consid-ered GCs as the best approximation ofSimple Stellar Populations, i.e. groups ofcoeval stars with the same chemical abun-dance, has been questioned in recent years.Apart from the blatant, peculiar case of ωCen, stars in any given GC share the samemetallicity only as far as heavy elements

The Messenger 11748

Figure 2: Hα linesafter subtraction of atemplate observedprofile, for the 13stars observed withUVES and brighterthan V=14.0(logL/L0=2.88). Thesolid lines show thedifferences of theobserved profiles, thedotted red lines showthe differences of thecorresponding theo-retical profiles.

Figure 3: Spectrum synthesis of the Na D1 and D2 lines in two RGB stars. Open squares arethe observed spectrum, while lines represent the synthetic spectra computed for appropriatevalues of temperature and 3 different sodium abundances: [Na/Fe]=0.4 (blue), 0.6 (green) and0.8 (red) dex. All abundances are given in the LTE assumption.

(i.e. those belonging to the Fe group) areconcerned. On the contrary, lighter elements(in primis carbon and nitrogen) show signif-icant abundance variations along the RGB,and even among unevolved main sequenceand turn-off stars. Sodium and oxygen abun-dances are anti-correlated among the firstascent RGB stars in almost all the GCs sur-veyed, for at least one magnitude below theRGB tip. This Na-O anticorrelation has beendetected also among turn-off stars in threeGCs so far, i.e. NGC 6397, NGC 6752 and47 Tuc, where both Na-rich/O-poor and Na-poor/O-rich stars are present. These anom-alies are found only in cluster stars, whereasthe abundance pattern of field stars is wellexplained by the classical scenario of a firstdredge-up and a second mixing episode tak-ing place above the magnitude level of theRGB bump. We refer the reader to Gratton etal. (2004) for a recent and comprehensivereview of this intricate subject.

The presence of these abundance varia-tions and anticorrelation in RGB stars indi-cates that both the CN-cycle and the ON-cycle (of the complete CNO H-burningcycle) are at work in GC stars. In particular,the proton-capture fusion mechanism, takingplace in the same (inner) regions where hightemperatures are reached and O is trans-formed in N, is able to produce Na from22Ne, as indicated by the Na-O anticorrela-tion. The products of these nucleo-synthesismechanisms are then brought to the surfaceby the convective motions in the red giantextended atmospheres. However, the pres-ence of these abundance variations inunevolved stars cannot be explained this

way. These stars do not have the physicalcharacteristics needed to produce theobserved abundance pattern, namely centralhigh temperatures (to produce these ele-ments in the observed proportions) andextended convective envelopes (to bringthem to the surface by internal mixing).Therefore, this pattern must be due to pre-existing abundance variations. Among thepossible sources of primordial contamina-tion, a previous generation of intermediate-mass AGB stars has been proposed, thatmight have polluted with Na-rich, O-poorejecta the material from which the subse-quent generation of stars was formed. Mostlikely, the overall chemical pattern observedin GC stars requires a contribution of bothprimordial contamination and evolutionarymixing. The debate seems presentlyfocussed on how to disentangle primordialvariations and subsequent evolutionaryeffects, and to properly ascertain their rela-tive proportions in a given cluster and inclusters of different physical properties (HBmorphology, density, age, metallicity, etc.).This, of course, requires the accurate knowl-edge of chemical abundances for a largenumber of GCs and for many stars withineach cluster. For this reason the use ofFLAMES is especially important, and hasled to very interesting results in NGC 2808.We show in Fig. 3 an example of Na I Dlines that were analysed with spectral syn-thesis techniques to derive the Na abun-dances. Similarly, O abundances werederived.

The [Na/Fe] abundances thus derivedare shown in Fig. 4. The histograms of theabundances, plotted separately for the 11brightest stars (logg≤1.02) and the 70fainter ones (log g > 1.02), reveal a similarspread in the distributions, and slightlylower average values for the brighter group.The spread in the distribution is thereforeindependent of luminosity and most likely ofprimordial origin, whereas the averageabundance value, that depends on luminosi-ty, is likely due to internal mixing phenome-na. So it seems that the [Na/Fe] abundance

variations found in NGC 2808 are mostlyprimordial, with some noise added by evolu-tionary effects. We show for comparison theresults obtained in M13, where the situationis similar except that the brighter stars havehigher values of [Na/Fe] than the fainterstars. Incidentally, a comparison with otherclusters, i.e. M5, M15 and M92, not shownhere, where the average [Na/Fe] abundancevalues do not vary significantly with lumi-nosity, indicates that in these latter clustersthe [Na/Fe] abundance variations detectedalong the RGB are likely of primordial ori-gin. In Fig. 5 we show the anticorrelated[Na/Fe] and [O/Fe] abundances for the 20stars analysed in NGC 2808 (red dots), andfor comparison the analogous data for M13(blue dots). In both clusters the anticorrela-tion is clear and well defined, and very O-poor stars are present.

To conclude, we note that this is the firsttime that such a large sample of RGB starshave been observed in any given GC withhigh resolution spectroscopy. This surveyhas allowed us to assess that mass loss mayindeed be present along the RGB, and totrace the occurrence and onset of this phe-nomenon down to fainter luminosity thresh-olds than previously estimated. These resultsare important for a better understanding ofthe subsequent stellar evolutionary phases,in particular of the peculiar HB morphologyof NGC 2808. The chemical inhomo-geneities detected in these stars seem to bemostly due to a previous generation of inter-mediate mass stars, as has been found also inother clusters. This has important conse-quences for a better understanding and mod-elling of GC formation processes.

RREFERENCESEFERENCESBedin et al. 2000, A&A 363, 159Cacciari, C., et al. 2003, A&A 413, 343 Carretta, E., et al. 2003, A&A 410, 143 Carretta, E., et al. 2004, ApJ 610, L25 Dupree, A. K. 1986, Ann. Rev. A&A 24, 377 Gratton, R., et al. 2004, Ann. Rev. A&A 42, 385Kraft et al. 1997, AJ 113, 279 Pasquini, L., et al. 2002, ESO Messenger 110, 1 Renzini, A. & Fusi Pecci, F. 1988, Ann. Rev. A&A

26, 199

© ESO - September 2004 49Cacciari C. et al., FLAMES spectroscopy of RGB stars in NGC 2808

Figure 4: [Na/Fe] abundance histograms forthe NGC2808 RGB stars, shown separatelyfor the brightest stars (log g ≤1.02) and thefainter ones (logg>1.02). Similar data for M13(Kraft et al. 1997) are shown for comparison.

Figure 5: [Na/Fe]vs [O/Fe] for theRGB stars inNGC2808 (reddots) compared toM13 (blue dots).

The Messenger 11750

DDATING STARS, in particularthe oldest ones, is one ofthe challenges for stellarastronomers. By datingthem, we can, for instance,

test evolutionary theories and set lower lim-its to the age of the Galaxy and of theUniverse. The most common approach todating involves the determination of a star’sage, that is, the time elapsed from its birth tothe present.

We present here an orthogonal perspec-tive, investigating if it is possible for the old-est stars to provide a reliable measurementof the time elapsed between the beginning ofstar formation in the Galaxy and the birth ofthese objects.

In order to achieve this goal we need atracer which, at least in the early Galaxy,was growing steadily (possibly slowly) andhomogeneously, not suffering from inhomo-geneities which may have been present,given the limited time available for an effi-cient mixing to occur.

Such a tracer is 9Be. Unlike most ele-ments, which are produced either in stars orby big bang nucleosynthesis, in fact, 9Be(together with B and the 6Li isotope) canonly be produced in the interstellar medium

by Galactic Cosmic Rays (GCRs) throughthe spallation of heavier nuclei, such as car-bon, oxygen and nitrogen (Reeves et al.1970). In the early Galaxy, Be was producedby energetic particles generated in SNexplosions and transported globally on aGalactic scale; its abundance is predicted toincrease uniformly with time, showing lessscatter than the products of stellar nucle-osynthesis such as Fe or O. The dominantspallation process is expected to be the socalled “primary” process, where Be is pro-duced by the collisions of accelerated C,N,Onuclei in Galactic Cosmic Rays with inter-stellar medium (ISM) protons and α-parti-cles. This process is called primary becauseit is expected to lead to a linear dependenceof Be on metallicity. A tight trend betweenBe and metallicity has been confirmedobservationally down to [Fe/H] ≅ –3.3 inmetal-poor field halo stars (Gilmore et al.1992, Molaro et al. 1997, Boesgaard et al.1999). This makes Be a potentially powerful“cosmic clock” for dating the first stages ofGalactic halo evolution (Suzuki et al. 2001).

To test Be as a cosmic clock it is neces-sary to measure Be in stars which can bedated independently. In this respect stars inold globular clusters, such as NGC 6397, are

ideal candidates, because their ages can bedetermined in a reliable way through, forinstance, main sequence fitting and stellarevolutionary theory, and they have beenshown to be formed within ~1 Gyr after theBig Bang (Gratton et al. 2003).

However, the search for Be poses sever-al challenges, because the only available Belines are the Be II resonance doublet at 313.1nm. This wavelength is very close to theatmospheric cut-off at 300 nm and the ter-restrial atmosphere heavily absorbs theincoming radiation, making observationsvery challenging. In addition, the Be linesare very weak and the spectral region aroundthem very crowded, so that high spectral res-olution is necessary.

The high UV efficiency of UVES at theVLT telescope Kueyen has opened a newpossibility, allowing for the first time thedetection of Be in two turn-off (TO) stars inNGC 6397. It is essential to reach the clusterTO because these stars are the most suitablefor Be analysis; in fact it must be borne inmind that Be may be destroyed in the stellarinteriors at temperatures above ~3.5 millionK, that is at temperatures about 1 million Khigher than the more fragile Li. Previousstudies of this cluster (Bonifacio et al. 2002)

VLVLT T OOBSERBSERVVAATIONSTIONS OFOF BBERERYLLIUMYLLIUM ININAA GGLOBULARLOBULAR CCLUSTERLUSTER: :

AA CLOCKCLOCK FORFOR THETHE EARLEARLYY GGALAXYALAXY ANDAND NEWNEW INSIGHTSINSIGHTS INTOINTO

GGLOBULARLOBULAR CCLUSTERLUSTER FORMAFORMATIONTION

THE FIRST-EVER MEASUREMENT OF THE BERYLLIUM CONTENT IN TWO STARS OF A GLOBULAR CLUSTER OBTAINED

WITH UVES AT THE VLT SHOWS THAT BERYLLIUM CAN BE USED AS A POWERFUL COSMOCHRONOMETER TO

DATE THE OLDEST STARS. IN THIS WAY WE ESTIMATE THAT THE GLOBULAR CLUSTER NGC 6397 FORMED

0.2–0.3 GYRS AFTER THE ONSET OF STAR FORMATION IN THE MILKY WAY. ASSUMING THAT THIS STARTED

SHORTLY AFTER THE BIG BANG (13.7 GYRS AGO ACCORDING TO WMAP), AND THE SUBSEQUENT “DARK AGES”WHICH ARE THOUGHT TO LAST ABOUT 0.2 GYR, THE NGC 6397 STARS WERE THEREFORE BORN

~13.2–13.3 GYRS AGO, A RESULT WHICH IS CONSISTENT WITH THE AGE OF THE CLUSTER AS INDEPENDENTLY

DERIVED FROM MAIN SEQUENCE FITTING. THIS CONSISTENCY WOULD INDICATE A REMARKABLE AGREEMENT

BETWEEN STELLAR EVOLUTION, COSMIC-RAY NUCLEOSYNTHESIS AND COSMOLOGY. THE UVES SPECTRA PROVE

AS WELL THAT THE GAS WHICH FORMED THE STARS MUST HAVE GONE THROUGH CNO PROCESSING IN THE

PROTOCLUSTER CLOUD BEFORE THEIR FORMATION.

L. PL. PASQUINIASQUINI 11, P, P. B. BONIFONIFACIOACIO 22, S. R, S. RANDICHANDICH 33, D. G, D. GALLIALLI 33, R. G. G, R. G. GRARATTONTTON 44

1EUROPEAN SOUTHERN OBSERVATORY, GARCHING BEI MÜNCHEN, GERMANY2ISTITUTO NAZIONALE DI ASTROFISICA, OSSERVATORIO ASTRONOMICO DI TRIESTE, ITALY

3ISTITUTO NAZIONALE DI ASTROFISICA, OSSERVATORIO ASTROFISICO DI ARCETRI, ITALY4ISTITUTO NAZIONALE DI ASTROFISICA, OSSERVATORIO ASTRONOMICO DI PADOVA, ITALY

have shown that these TO stars have anabundance of Li as high as the primordialvalue. Since this more fragile element is atits original level, then, a fortiori, Be has notbeen depleted in their atmospheres.

Conversely, brighter subgiants in the samecluster show clear evidence of Li dilution.Even if NGC 6397 is the second closestcluster, its TO is still relatively faint, placedat an apparent magnitude of V~16. This

means that a jump of almost 3 magnitudeswith respect to the faintest star previouslyobserved for Be abundance determinationwas necessary. Even with UVES and theVLT it has been necessary to expose eachstar for 10.5 hours.

The observed spectra in the regionaround the BeII lines are shown in Figure 1,together with the best-fit synthetic spectra.Thanks to the high resolution (R=45,000)and signal-to-noise ratio (8.5 and 15) of thespectra, the two Be II lines are clearlydetected and measurable in both stars. Theresulting abundance is very similar for bothstars, and we obtain log (Be/H) =–12.35±0.2(where errors include uncertainties in theadopted gravity). The log (Be/H) retrieved isin excellent agreement with that of fieldstars with similar [Fe/H] abundances. In thesame figure the spectrum of a brighter fieldstar is also shown, which has parameterssimilar to the targets and is used as a controlstar.

The measured Be abundance of the twotargets is plotted in figure 2, together withthe time evolution of Be resulting from amodel of chemical evolution following theenrichment of three different regions in theGalaxy, coupled by mass flows: the halo, thethick disk and the thin disk (Valle et al.2002). The other data point in the Figureshows the Be abundance in the Sun and inthe young open cluster IC 2391, an indicatorof the present-day value. In this Figure, starformation in the Galaxy is assumed to start13.7 Gyr ago. This value represents the ageof the Universe (time elapsed from the BigBang) according to WMAP (Bennet et al.2003). A more realistic age of the galaxyshould take into account the time intervalbetween the Big Bang and the epoch of re-ionization. The best estimate for this intervalis 0.18 Gyr (WMAP data), well within theerrors on the age estimate of NGC 6397.

The inset in Fig. 2 shows the halo evolu-tion of Be on a finer time scale, with the twohorizontal lines limiting the 1σ range of Beabundance in NGC 6397. This plot empha-sizes the possible use of Be as a “cosmicclock”: the measured value of Be indicatesthat the formation of NGC 6397 occurredabout 0.2–0.3 Gyr after the onset of star for-mation in the Galactic halo. Given the uncer-tainty in the model assumptions, it is safe toconclude that the birth of the stars compos-ing NGC 6397 took place within the first~0.5 Gyr of halo evolution, in agreementwith the main-sequence dating of the cluster.In fact under the previous assumptions, the“Beryllium age” retrieved for the cluster is13.45 Gyr, which is in very good agreementwith the absolute age of 13.4 ± 0.8 ±0.6 Gyr, recently derived on the basis of themain sequence fitting method with standardisochrones (Gratton et al. 2003). Althoughthe almost exact coincidence between thetwo “ages” is fortuitous, the combination of


Figure 1: UVES spec-tra of the two turn-offstars of the Globularcluster NGC 6397:A2111 and A228. Thered dots are the best-fitting synthetic spec-tra which correspondto Log(Be/H)= –12.27for A228 and –12.43for A2111. For com-parison, the spectrumof the bright halo starHD 218502, whoseatmospheric parame-ters are close to thoseof the NGC 6397 turn-off stars, is alsoshown. The best fitsynthetic spectrum forthis star correspondsto Log(Be/H)=–12.36.

Figure 2: Evolution of Be with time in the Galaxy according to a three-zone Galactic chemicalevolution model (Valle et al. 2002). The three curves refer to the halo, thick disc, and thin disc.The data points show the Be abundance in the young open cluster IC 2391 (age 50 Myr), theSun (age 4.55 Gyr), and the globular cluster NGC 6397 (age 13.4±0.8 Gyr). The model resultis normalized to the solar meteoritic abundance. The inset illustrates the use of Be as a “cos-mic clock” to constrain the formation of NGC 6397. The horizontal lines corresponds to the 1σcontours around the measured Be abundance. The cluster birth is constrained to the first0.2–0.3 Gyr after the onset of star formation in the Galactic halo.

the evolutionary and of the Be age clearlyshow that the halo of the Galaxy must haveformed shortly after the Big bang.

MMOREORE EXCITINGEXCITING RESULRESULTSTSABOUTABOUT THETHE CCLUSTERLUSTER

Many Globular Clusters show peculiar pat-terns in their chemical composition, whichare not observed among field stars and aretherefore clearly related to the peculiarGlobular Cluster environment. Although thisanomaly was first discovered more than 30years ago, no clear answer yet exists for itsorigin. The superb UVES spectra, thanks tothe combination of resolving power, signalto noise and spectral coverage, add somesignificant new results on this topic. In addi-tion to the Beryllium lines, we also observedimportant bands of Nitrogen in the UV andthe Oxygen triplet in the near infrared.

While the rest of the elements show animpressively constant value in NGC 6397stars, our spectra show that the two observedstars have a difference of up to 0.6 dex intheir O abundance, and a rather high N con-tent ([N/Fe]~1.3) with respect to field starsof similar metallicity. We also confirm thatthe average oxygen level is low with respectto that of field stars of similar metallicity, asfound by Gratton et al. 2003.

Figures 3 and 4 shows the spectraaround the Oxygen triplet and the NH

regions respectively. In figure 3 the differ-ence in the Oxygen line strength among thetwo stars is evident, while in figure 4 thecomparison between the two cluster starsand the similar field star HD218502 showsclearly how much stronger the NH band inthe cluster stars is with respect to the fieldobject.

This abundance pattern suggests that thestars of NGC 6397 were either formed from,or partially polluted by, material bearing thesignature of the products of stellar nucle-osynthesis, such as that occurring in massiveasymptotic giant-branch (AGB) stars(Ventura et al. 2002). In this phase, stellarmaterial is processed at very high tempera-tures (~108 K) where O is effectively burntto N in the CNO cycle and then returned tothe ISM by mass loss. This process couldexplain both the low O and the high N val-ues observed, while most other elementswould conserve their previous abundances.However, at the high temperatures charac-terizing AGB nucleosynthesis, Li and Be arecompletely destroyed. The normal Pop IIstars level of Li observed in NGC 6397(Bonifacio et al. 2002) could have beenrestored during this AGB phase because Liis predicted to be produced by AGB starsand could be brought to the surface from theinterior through the so called Cameron-Fowler mechanism: convective cells bring

up to the surface freshly synthesized Libefore it is destroyed. Of course this hypoth-esis requires a remarkable fine-tuningbetween Li production and destruction.However the special nature of 9Be meansthat this element cannot be synthesized instars, but that it is only destroyed during theAGB phase, and our observations thereforeseem to be at variance with this picture.Thus, our detection of Be rules out the pos-sibility that a considerable fraction of the gasof the protocluster was processed by a previ-ous generation of AGB stars, unless the gaswas processed extremely early in these starsand immediately released back to the ISM,where it was exposed to the Galactic CosmicRays.

RREFERENCESEFERENCESBennett, C. L., Halpern, M., Hinshaw, G., et al.

2003, ApJSS 148, 1 Boesgaard, A. M. et al. 1999, AJ 117, 1549 Bonifacio, P., Pasquini, L. et al. 2002, A&A 390,

91 Gilmore, G. et al. 1992, Nature 357, 379 Gratton, R. G., et al. 2003 A&A 408, 529 Molaro, P. et al. 1997, A&A, 319, 593 Reeves, H., Fowler, W. A., Hoyle, F. 1970, Nature

226, 727 Suzuki, T. K., Yoshii, Y. 2001, ApJ 549, 303 Valle, G., Ferrini, F., Galli, D. Shore, S. N. 2002,

ApJ 566, 252 Ventura, P., D’Antona, F., Mazzitelli, I. 2002,

A&A 393, 215

The Messenger 11752

Figure 3: UVESspectra of the

two NGC 6397stars in the

region of theOxygen triplet.The two starshave identical

stellar parame-ters but clearly

different linestrengths; theirO abundances

differ by almost0.6 dex.

Figure 4: UVES spectra of the two NGC 6397 stars and of thecomparison field star HD218502 in the region around the NH band

at 336 nm. The band is very well pronounced in the two globularcluster stars, while it is virtually absent in the reference star, indicat-

ing the strong N overabundance in the NGC 6397 stars.


FFOR ALMOST A CENTURY,Cepheids have occupied a cen-tral role in distance determina-tions. This is thanks to theexistence of the Period-

Luminosity relation M = a log P + b whichrelates the logarithm of the variability periodof a Cepheid to its absolute mean magni-tude. These stars became even more impor-

tant since the HST Key Project on the extra-galactic distance scale has totally relied onCepheids for the calibration of distance indi-cators to reach cosmologically significantdistances. In other words, if the calibrationof the Cepheid P-L relation is wrong, thewhole extragalactic distance scale is wrong.

There are various ways to calibrate theP-L relation. The avenue chosen by the HST

Key Project was to assume a distance to theLarge Magellanic Cloud (LMC), therebyadopting a zero point for the distance scale,but the LMC distance is currently the weaklink in the extragalactic distance scale lad-der. Another avenue is to determine the zeropoint of the Period-Luminosity relation withGalactic Cepheids, using for instance paral-lax measurements, Cepheids in clusters, orthrough the Baade-Wesselink (BW) method(see e.g. Bersier et al. 1997). We proposed inthe present work to improve the calibrationof the Cepheid Period-Radius (P-R), Period-Luminosity (P-L) and surface brightness-color (SB) relations through the combinationof spectroscopic and interferometric obser-vations of bright Galactic Cepheids.

TTHEHE INTERFEROMETRICINTERFEROMETRIC BBAADEAADE--WWESSELINKESSELINK METHODMETHOD

The basic principle of the BW method is tocompare the linear and angular size variationof a pulsating star, in order to derive its dis-tance through a simple division. Thismethod is a well-established way to deter-mine the luminosity and radius of a pulsat-ing star. Figure 1 illustrates the two quanti-ties measured for this technique: the radiusvariation curve (left part), that is integratedfrom the radial velocity curve, and theangular diameter variation, measured byinterferometry.

On one hand, the linear size variationcan be obtained by high resolution spec-troscopy, through the integration of the radi-al velocity curve obtained by monitoring theDoppler shift of the spectral lines present inthe spectrum. A difficulty in this process isthat the measured wavelength shifts are inte-

CCEPHEIDEPHEID PPULSAULSATIONSTIONS RRESOLESOLVEDVED

BYBY THETHE VLVLTITITHE VERY HIGH SPATIAL RESOLUTION PROVIDED BY THE VLTI MAKES IT POSSIBLE TO MEASURE DIRECTLY THE

CHANGE IN ANGULAR DIAMETER OF SEVERAL SOUTHERN CEPHEIDS OVER THEIR PULSATION CYCLE. WHEN

COMBINED WITH RADIAL VELOCITY MEASUREMENTS, THIS ALLOWED US TO MEASURE PRECISELY THEIR DISTANCES

IN A QUASI-GEOMETRICAL WAY. THIS IS ESSENTIAL INFORMATION TO CALIBRATE THE CEPHEID’S PERIOD-LUMINOSITY LAW, AS WELL AS THE PERIOD-RADIUS AND SURFACE BRIGHTNESS-COLOUR RELATIONS.

PP. K. KERERVELLAVELLA 11, D. B, D. BERSIERERSIER 22, N. N, N. NARDETTOARDETTO 33, , D. MD. MOURARDOURARD 33, P, P. F. FOUQUÉOUQUÉ 44, V, V. C. COUDÉOUDÉ DUDU FFORESTOORESTO 11

1 OBSERVATOIRE DE PARIS, FRANCE2 SPACE TELESCOPE SCIENCE INSTITUTE, USA3 OBSERVATOIRE DE LA CÔTE D’AZUR, FRANCE

4 OBSERVATOIRE MIDI-PYRÉNÉES, FRANCE

Figure 1: The two observational techniques used for the interferometric version of the BWmethod are high resolution spectroscopy (left) and interferometry (right). The former providesthe radial velocity curve over the pulsation cycle of the star. Once integrated, this provides thelinear radius variation of the star (in metres). The interferometric observations give access tothe angular radius variation of the star. The ratio of these two quantities gives the distance ofthe Cepheid.

grated values over the full stellar disc. Toconvert them into a pulsation velocity, i.e. aphysical displacement of the photosphere atthe center of the disc, we have to multiply itby a projection factor p that encompasses thesphericity of the star and the structure of itsatmosphere (limb darkening,…). Unfor-tunately, the p-factor is still uncertain at alevel of a few percent but classical high res-olution spectroscopy coupled with the dis-persed fringes mode of AMBER are expect-ed to bring strong constraints on this impor-tant factor. We have also started a theoreticalapproach in order to strongly constraint thisparameter and to improve our distance deter-minations (Nardetto et al. 2004).

On the other hand, the angular size isdifficult to estimate directly. Until recently,the only method to estimate the angular sizewas through the surface brightness of thestar. With the advent of powerful infraredlong baseline interferometers, it is now pos-sible to resolve spatially the star itself, andthus measure directly its photospheric angu-lar diameter. An uncertainty at a level ofabout 1% remains on the limb darkening ofthese stars, that is currently taken from stat-ic atmosphere models. In the near future,the gain in spatial resolution brought by theshort wavelength modes of AMBER (J andH bands) will allow us to measure directlythe intensity profile of several Cepheids.

OOBSERBSERVVAATIONSTIONS WITHWITH VINCI VINCI ANDANDTHETHE VLVLTI TTI TESTEST SSIDEROSTIDEROSTAATSTS

For our observations, the beams from thetwo VLTI Test Siderostats (0.35m aperture)or the two Unit Telescopes UT1 and UT3were recombined coherently in VINCI, theVLTI Commissioning Instrument. We used aregular K band filter (λ = 2.0–2.4 µm) thatgives an effective observation wavelength of2.18 µm for the effective temperature of typ-ical Cepheids. Three VLTI baselines wereused for this program: E0-G1, B3-M0 and

UT1-UT3 respectively 66, 140 and 102.5min ground length. Figure 2 shows their posi-tions on the VLTI platform.

In total, we obtained 69 individual angu-lar diameter measurements, for a total ofmore than 100 hours of telescope time (2hours with the UTs), spread over 68 nights(Kervella et al. 2004a). One of the keyadvantages of VINCI is to use single-modefibres to filter out the perturbations inducedby the turbulent atmosphere. The resultinginterferograms are practically free of atmos-pheric corruption, except the piston mode(differential longitudinal delay of the wave-

front between the two apertures) that tendsto smear the fringes and affect their visibili-ty. But this residual can be brought down toa very low level by using a fast acquisitionrate. As a result, the visibility measurementsfrom VINCI are currently the most preciseever obtained, with a relative statistical dis-persion that can be as low as 0.05% onbright stars.

SSELECTEDELECTED SAMPLESAMPLE OFOF CCEPHEIDSEPHEIDSDespite their apparent brightness, Cepheidsare located at large distances, and ESA’sHipparcos satellite could only obtain a limit-ed number of Cepheid distances with a rela-tively poor precision. If we exclude thepeculiar first overtone pulsator Polaris, theclosest Cepheid is δ Cep, located at approx-imately 250 pc. Using the interferometricBW technique, it is possible to derive direct-ly the distance to the Cepheids for which wecan measure the amplitude of the angulardiameter variation. Even for the nearbyCepheids, this requires an extremely highresolving power, as the largest Cepheid inthe sky, L Car, is only 0.003) in averageangular diameter. Long baseline interferom-etry is therefore the only technique thatallows us to resolve these objects.

The capabilities of the VLTI for theobservation of nearby Cepheids are out-standing, as it provides long baselines (up to202m) and thus a high resolving power.Though they are supergiant stars, theCepheids are generally very small objects interms of angular size. A consequence is that

The Messenger 11754

Figure 2: View of the Paranal platform with the three baselines usedfor the VLTI observations of Cepheids (in red).

Figure 3: VINCI observations of the pulsation of L Car (P = 35.5 days, red dots) and theadjusted radius curve (green line), as deduced from the integration of the radial velocitymeasured on this star over its pulsation.

the limit on the number of interferometrical-ly resolvable Cepheids is not set by the sizeof the light collectors, but by the baselinelength. From photometry only, several hun-dred Cepheids can produce interferometricfringes using the VLTI Auxiliary Telescopes(1.8m aperture). However, in order to meas-ure accurately their size, one needs toresolve their disc to a sufficient level, andthis reduces the total number of accessibleCepheids to about 30.

Considering the usual constraints interms of sky coverage, limiting magnitudeand accessible resolution, we selected sevenbright Cepheids observable from ParanalObservatory (latitude –24 degrees): X Sgr, ηAql, W Sgr, β Dor, ζ Gem, Y Oph and L Car.The periods of these stars cover a widerange, from 7 to 35.5 days, an importantadvantage to properly constrain the P-R andP-L relations. Using the interferometric BWmethod, we derived the distances to η Aql,W Sgr, β Dor and L Car. For the remainingthree objects of our sample, X Sgr, ζ Gemand Y Oph, we obtained average values oftheir angular diameters, and we applied ahybrid method to derive their distances,based on published values of their lineardiameters. Figure 3 shows the angular diam-eter curve and the fitted radius curve of LCar (P = 35.5 days), that constrains its dis-tance to a relative precision better than 5%.A discussion of these data can be found inKervella et al. (2004d).

PPERIODERIOD-R-RADIUSADIUS RELARELATIONTIONThe Period-Radius relation (P-R) is animportant constraint to the Cepheid models(see e.g. Bono et al. 1998). It takes the formof the linear expression log R = a log P + b.In order to calibrate this relation, we need toestimate directly the linear radii of a set ofCepheids. To complement the VINCI sam-ple of seven Cepheids, we added the meas-urements of δ Cep, ζ Gem and η Aqlobtained previously by other interferome-ters. We have applied two methods to deter-mine the radii of the Cepheids of our sam-ple: the interferometric BW method, and acombination of the average angular diameterand trigonometric parallax. While the firstprovides directly the average linear radiusand distance, we need to use trigonometricparallaxes to derive the radii of the Cepheidsfor which the pulsation is not detected. Forthese stars, we applied the Hipparcos dis-tance, except for δ Cep, for which we con-sidered the recent parallax measurement byBenedict et al. (2002).

Figure 4 shows the distribution of themeasured diameters on the P-R diagram.When we choose to consider a constantslope of a=0.750±0.024, as found by Gieren,Fouqué & Gómez (1998, hereafter GFG98),we derive a zero point of b=1.105±0.029(Kervella et al. 2004b). As a comparison,GFG98 obtained a value of b=1.075±0.007,

© ESO - September 2004 55Kervella P. et al., Cepheids pulsations resolved by the VLTI

Figure 4: Period-Radius relation deduced from the interferometric measurements ofCepheids. The blue line corresponds to the simultaneous fit of both the zero point andslope of the line. The orange dashed line assumes the slope from GFG98, fitting only thezero point.

Figure 5: Period-Luminosity relation in the V band, as deduced from the interferometric obser-vations of Cepheids and the HST parallax measurement of δ Cep. The green line is the fittedP-L relation, assuming the slope from GFG98. The agreement between the model and themeasurements is excellent, in particular for the high precision measurements of δ Cep and LCar.

only –1.6σ away from our result. Theserelations are compatible with our calibrationwithin their error bars. Fitting simultaneous-ly both the slope and the zero point to ourdata set, we obtain a=0.767±0.009 andb=1.091±0.011. These values are only ∆a =+0.7σ and ∆b= +1.2σ away from the GFG98calibration. Considering the limited size ofour sample, the agreement is very satisfacto-ry. On the other hand, the slopes derivedfrom numerical models of Cepheids are sig-nificantly different, such as the slopea=0.661±0.006 found by Bono et al. (1998).

PPERIODERIOD-L-LUMINOSITYUMINOSITY RELARELATIONTIONThe Cepheid P-L relation is the basis of theextragalactic distance scale, but its calibra-tion is still uncertain at a ∆M = ±0.10 maglevel. Moreover, it is not excluded that a sig-nificant bias of the same order of magnitudeaffects our current calibration of this rela-tion. Until now, the classical BW method

(where one combines photometry and radialvelocity data) was used to obtain the dis-tance and radius of a Cepheid. A recentapplication of this method to individual starscan be found for instance in Taylor & Booth(1998). A requirement of this method is avery accurate measurement of the Cepheid’seffective temperature at all observed phases,in order to determine the angular diameter.Interferometry allows us to bypass this stepand its associated uncertainties by measur-ing directly the variation of angular diameterduring the pulsation cycle. The latest gener-ation of long baseline visible and infraredinterferometers has the potential to provideprecise distances to Cepheids up to about1 kpc, using the interferometric BW method.

Our sample is currently too limited toallow a robust determination of the P-L rela-tion, defined as Mλ= αλ (log P – 1) + βλ thatwould include both the slope and thelog P = 1 reference point βλ. However, if we

suppose that the slope is known a priorifrom the literature, we can still derive a pre-cise calibration. We have considered for ourfit the P-L slope measured on LMCCepheids. This is a reasonable assumption,as it was checked successfully on theMagellanic Clouds Cepheids, and in addi-tion our sample is currently too limited toderive both the slope and the reference pointsimultaneously.

For the V band, we obtain βV=–4.209±0.075 (Kervella et al. 2004b). Thepositions of the Cepheids on the P-L dia-gram are shown on Fig. 5. Our calibrationsdiffer from GFG98 by ∆βV = +0.14 mag,corresponding to +1.8σ. The sample is dom-inated by the high precision L Car and δCep measurements. When these two starsare removed from the fit, the difference withGFG98 is slightly increased, up to +0.30mag, though the distance in σ units isreduced (+1.5). From this agreement, L Carand δ Cep do not appear to be systematical-ly different from the other Cepheids of oursample. It is difficult to conclude firmly thatthere is a significant discrepancy betweenGFG98 and our results, as our sample is cur-rently too limited to exclude a small-statis-tics bias. However, if we assume an intrinsicdispersion of the P-L relation σPL~ 0.1 mag,as suggested by GFG98, then our resultspoint toward a slight underestimation of theabsolute magnitudes of Cepheids by theseauthors. On the other hand, we obtain pre-cisely the same log P = 1 reference pointvalue in V as Lanoix et al. (1999) did, usingparallaxes from Hipparcos. The excellentagreement between these two fully inde-pendent, geometrical calibrations of the P-Lrelation is remarkable.

Averaging our K and V band zero pointvalues, we obtain a final LMC distancemodulus of µ0 = 18.55 ± 0.10. This value isstatistically identical to the LMC distanceused for the HST Key Project, µ0 = 18.50 ±0.10. We would like to emphasize that thisresult is based on six stars only, and our sam-ple needs to be extended in order to excludea small-number statistics bias. In this sense,the P-L calibration presented here should beconsidered as an intermediate step toward afinal and robust determination of this impor-tant relation by interferometry.

SSURFURFACEACE BRIGHTNESSBRIGHTNESS RELARELATIONSTIONSThe surface brightness (hereafter SB) rela-tions link the emerging flux per solid angleunit of a light-emitting body to its colour, oreffective temperature. Intuitively, the con-servation of the SB can easily be understoodas both the solid angle subtended by a starand its apparent brightness are decreasingwith the square of its distance. In theory, fora perfect blackbody emission, their ratio istherefore a constant for a given effectivetemperature. In practice, the stars are notperfect blackbodies, and we have to rely on

The Messenger 11756

Figure 6: Surface brightness-colour relation FV(V-K) of Cepheids (upper part) and the residu-als of the fit (lower part). The 145 individual interferometric measurements are displayed as reddots, and the fitted linear model as a green line.

a colour index (i.e. the difference betweenmagnitudes in two photometric bands) as atracer of the effective temperature.

The SB relations are of considerableastrophysical interest for Cepheids, as awell-defined relation between a particularcolour index and the surface brightness canprovide accurate predictions of their angulardiameters. When combined with the radiuscurve, integrated from spectroscopic radialvelocity measurements, they give access tothe distance of the Cepheid through the clas-sical (non interferometric) BW method. Thismethod has been applied recently toCepheids in the SMC (Storm et al. 2004),i.e. at a far greater distance than what can beachieved by the interferometric BW method.But the accuracy that can be achieved on thedistance estimate is conditioned for a largepart by our knowledge of the SB relations.

When considering a perfect blackbodycurve, any colour can in principle be used toobtain the SB, but in practice, the linearity ofthe correspondance between log Teff andcolor depends on the chosen wavelengthbands. The surface brightness Fλ is given bythe following expression (Fouqué & Gieren1997) : Fλ = 4.2207 – 0.1 mλ - 0.5 log qLDwhere qLD is the limb darkened angulardiameter, i.e. the angular size of the stellarphotosphere. To fit the individual measure-ments, we used a linear function of the stel-lar color indices, expressed in magnitudes(logarithmic scale), and SB relations can befitted using for example the followingexpression: FV(V-K) = a (V-K)0 + b. The aand b coefficients represent respectively theslope and zero point of the SB relation.

We assembled a list of 145 individualinterferometric measurements of Cepheids,related to nine stars. For each measurementepoch, we estimated the BVRIJHK magni-tudes based on Fourier interpolations of the

available photometric data from the litera-ture and corrected them for interstellarextinction.The resulting FV(V-K) relation fit is present-ed in Fig. 6. The other relations based on theV band surface brightness FV and BIJHKcolours are plotted on Fig. 7. The smallestresidual dispersions are obtained for theinfrared based colors, for instance:FV = –0.1336±0.0008(V–K)+3.9530±0.0006(Kervella et al. 2004c). The intrinsic disper-sion is undetectable at the current level ofprecision of our measurements, and could beas low as 1%.

PPROSPECTSROSPECTS WITHWITH AMBERAMBERWhile our present results are very encourag-ing, the calibration of the P-R and P-L rela-tions as described here may still be affectedby small systematic errors. In particular themethod relies on the fact that the displace-ments measured through interferometry andthrough spectroscopy (integration of theradial velocity curve) are in different units(milli-arcseconds and kilometers respective-ly) but are the same physical quantity. Thismay not be exactly the case, as the regions ofa Cepheid’s atmosphere where the lines areformed do not necessarily move homolo-gously with the region where the K-bandcontinuum is formed. The limb darkeningcould also play a role at a level of ~1%. Anexploration of these refined physical effectswill soon be possible with the high spectralresolution mode of the AMBER instrument.

The upcoming availability of 1.8mAuxiliary Telescopes on the VLTI platformin 2004, to replace the 0.35m TestSiderostats, will allow us to observe manyCepheids with a precision at least as good asour observations of L Car (Fig. 3). In addi-tion, the AMBER instrument will extend theVLTI capabilities toward shorter wave-

lengths (J and H bands), thus providinghigher spatial resolution than VINCI (Kband). The combination of these twoimprovements will extend significantly theaccessible sample of Cepheids, and weexpect that the distances to more than 30Cepheids will be measurable with a preci-sion better than 5%. This will provide a highprecision calibration of both the referencepoint (down to ±0.01 mag) and the slope ofthe Galactic Cepheid P-L. As the galaxieshosting the Cepheids used in the HST KeyProject are close to solar metallicity on aver-age, this Galactic calibration will allow us tobypass the LMC step in the extragalacticdistance scale. Its associated uncertainty of±0.06 due to the metallicity correction of theLMC Cepheids will therefore become irrele-vant for the measurement of the Hubble con-stant H0.

RREFERENCESEFERENCESBenedict, G. F., McArthur, B. E., Fredrick, L. W.,

et al. 2002, AJ, 123, 473Bersier, D., Burki, G., Kurucz, R.L. 1997, A&A,

320, 228Bono, G., Caputo, F., & Marconi, M. 1998, ApJ,

497, L43Gieren, W. P., Fouqué, P. & Gómez, M. 1998, ApJ,

496, 17 (GFG98)Kervella, P., Nardetto, N., Bersier, D., et al.

2004a, A&A, 416, 941Kervella, P., Bersier, D., Mourard, D., et al.

2004b, A&A, 423, 327Kervella, P., Bersier, D., Mourard, et al. 2004c,

A&A, in pressKervella, P., Fouqué, P., Storm, J., et al. 2004d,

ApJ, 604, L113Lanoix, P., Paturel, G. & Garnier, R. 1999,

MNRAS, 308, 969Nardetto, N., Fokin, A., Mourard, D. et al. 2004,

A&A, in pressStorm, J., Carney, B. W., Gieren, W. P., et al. 2004,

A&A, 415, 531Taylor, M. M. & Booth A. J. 1998, MNRAS, 298,

594

© ESO - September 2004 57Kervella P. et al., Cepheids pulsations resolved by the VLTI

Figure 7: Overview of the surface brightness-colour relations in the V band, based on the V-B(blue), V-I (yellow), V-J (orange), V-H (red) and V-K (dark red) colors.

The Messenger 11758

AASTRONOMY in the 21st centu-ry is facing the need for rad-ical changes. When dealingwith surveys of up to ~1,000sources, one could apply for

telescope time and obtain an optical spec-trum for each one of them to identify thewhole sample. Nowadays, we have to dealwith huge surveys (e.g., the Sloan DigitalSky Survey [SDSS], the Two Micron AllSky Survey [2MASS], the Massive CompactHalo Object [MACHO] survey), reaching(and surpassing) 100 million objects. Evenat, say, 3,000 spectra at night, which is onlyfeasible with the most efficient multi-objectspectrographs and for relatively brightsources, such surveys would require morethan 100 years to be completely identified, atime which is clearly much longer than thelife span of the average astronomer! Buteven taking a spectrum might not be enoughto classify an object. We are in fact reachingfainter and fainter sources, routinely beyondthe typical identification limits of the largesttelescopes available (approximately 25 magfor 2–4 hour exposures), which makes “clas-sical” identification problematic. These verylarge surveys are producing a huge amountof data: it would take about two months todownload at 1 Mbytes/s (a very good rate formost astronomical institutions) the DataRelease 2 SDSS images, about two weeksfor the catalogues. The images would fill upabout 1,000 DVDs. And the final SDSS willbe about three times as large. These data,once downloaded, need also to be analysed,which requires tools which may not be avail-able locally and, given the complexity ofastronomical data, are different for differentenergy ranges. Moreover, the breathtakingcapabilities and ultra-high efficiency of new

ground- and space-based observatories haveled to a “data explosion”, with astronomersworld-wide accumulating of the order of aTerabyte of data per night. Finally, onewould like to be able to use all of these data,including multi-million-object catalogues,by putting this huge amount of informationtogether in a coherent and relatively simpleway, something which is impossible atpresent.

All these hard, unescapable facts call forinnovative solutions. For example, theobserving efficiency can be increased by aclever pre-selection of the targets, whichwill require some “data-mining” to charac-terise the sources’ properties before hand, sothat less time is “wasted” on sources whichare not of the type under investigation. Onecan expand this concept even further andprovide a “statistical” identification of astro-nomical sources by using all the available,multi-wavelength information without theneed for a spectrum. The data-downloadproblem can be solved by doing the analysiswhere the data reside. And finally, easy andclever access to all astronomical data world-wide would certainly help in dealing withthe data explosion and would allowastronomers to take advantage of it in thebest of ways.

TTHEHE VVIRIRTUALTUAL OOBSERBSERVVAATORTORYYThe name of the solution is the VirtualObservatory (VO). The VO is an innovative,evolving system, which will allow users tointerrogate multiple data centres in a seam-less and transparent way, to best utiliseastronomical data. Within the VO, dataanalysis tools and models, appropriate todeal also with large data volumes, will bemade more accessible. New science will be

enabled, by moving Astronomy beyond“classical” identification with the character-isation of the properties of very faint sourcesby using all the available information. Allthis will require good communication, that isthe adoption of a common language betweendata providers, tool users and developers.This is being defined now using new inter-national standards for data access and min-ing protocols under the auspices of therecently formed International VirtualObservatory Alliance (IVOA: http://ivoa.net),a global collaboration of the world’s astro-nomical communities.

One could think that the VO will only beuseful to astronomers who deal with colossalsurveys and huge amounts of data. That isnot the case. The World Wide Web is equiv-alent to having all the documents of theworld inside one’s computer, as they are allreachable with a click of a mouse. Similarly,the VO will be like having all the astronom-ical data of the world inside one’s desktop.That will clearly benefit not only profession-al astronomers but also anybody interestedin having a closer look at astronomical data.Consider the following example: imagineone wants to find all the observations of agiven source available in all astronomicalarchives in a given wavelength range. Onealso needs to know which ones are in raw orprocessed format, one wants to retrieve themand, if raw, one wants also to have access tothe tools to reduce them on-the-fly. At pres-ent, this is extremely time consuming, if atall possible, and would require, even to sim-ply find out what is available, the use a vari-ety of search interfaces, all different fromone another and located at different sites.The VO will make all this possible veryeasily.

FFIRSTIRST SSCIENCECIENCE FORFOR THETHE

VVIRIRTUALTUAL OOBSERBSERVVAATORTORYY

THE VIRTUAL OBSERVATORY WILL REVOLUTIONISE THE WAY WE DO ASTRONOMY, BY ALLOWING EASY ACCESS

TO ALL ASTRONOMICAL DATA AND BY MAKING HANDLING AND ANALYSING DATASETS AT VARIOUS LOCATIONS

ACROSS THE GLOBE MUCH SIMPLER AND FASTER. WE REPORT HERE ON THE STATUS OF THE VIRTUAL

OBSERVATORY IN EUROPE AND ON THE FIRST SCIENCE RESULT COMING OUT OF IT, THE DISCOVERY OF ~30SUPERMASSIVE BLACK HOLES THAT HAD PREVIOUSLY ESCAPED DETECTION BEHIND MASKING DUST CLOUDS.

PPAOLOAOLO PPADOVADOVANIANI 11, M, MARKARK G. AG. ALLENLLEN 22, P, PIEROIERO RROSAOSATITI 33, N, NICHOLASICHOLAS A. WA. WALALTONTON 44

1ST-ECF, EUROPEAN SOUTHERN OBSERVATORY2CENTRE DE DONNÉS ASTRONOMIQUES DE STRASBOURG, FRANCE

3EUROPEAN SOUTHERN OBSERVATORY4INSTITUTE OF ASTRONOMY, CAMBRIDGE, UK

TTHEHE VO VO ININ EEUROPEUROPE: : THETHE AASTROPHYSICALSTROPHYSICAL

VVIRIRTUALTUAL OOBSERBSERVVAATORTORYY

The status of the VO in Europe is very good.In addition to seven current national VOprojects, the European funded collaborativeAstrophysical Virtual Observatory initiative(AVO: http://www.euro-vo.org) is creating thefoundations of a regional scale infrastructureby conducting a research and demonstrationprogramme on the VO scientific require-ments and necessary technologies. The AVOhas been jointly funded by the EuropeanCommission (under the Fifth FrameworkProgramme [FP5]) with six European organ-isations participating in a three year Phase-Awork programme. The partner organisationsare ESO in Munich, the European Space

Agency, AstroGrid (funded by PPARC aspart of the United Kingdom’s E-Science pro-gramme), the CNRS-supported Centre deDonnées Astronomiques de Strasbourg(CDS) and TERAPIX astronomical datacentre at the Institut d’Astrophysique inParis, the University Louis Pasteur inStrasbourg, and the Jodrell BankObservatory of the Victoria University ofManchester. The AVO is the definition andstudy phase leading towards the Euro-VO –the development and deployment of a fullyfledged operational VO for the Europeanastronomical research community.

The AVO project is driven by its strate-gy of regular scientific demonstrations ofVO technology, held on an annual basis incoordination with the IVOA. For this pur-

pose progressively more complex AVOdemonstrators are being constructed. Thecurrent one is an evolution of Aladin, devel-oped at CDS, and has become a set of vari-ous software components, provided by AVOand international partners, which allows rel-atively easy access to remote data sets,manipulation of image and catalogue data,and remote calculations in a fashion similarto remote computing.

The AVO held its second demonstration,“AVO 1st Science”, on January 27–28, 2004at ESO. The demonstration was truly multi-wavelength, using heterogeneous and com-plex data covering the whole electromagnet-ic spectrum. These included: MERLIN,VLA (radio), ISO [spectra and images] and2MASS (infrared), USNO, ESO 2.2m/WFI


Figure 2: An example of the direct links between imaging andspectral data: an obscured source selected via its X-ray(Chandra) properties, imaged by the HST/ACS, and identifiedthrough an ESO/VLT FORS2 spectrum (below) as a type 2quasar at redshift 3.06 (Szokoly et al. 2004). The great major-ity of our new QSO 2 candidates are too faint to be classifiedeven by the VLT or Keck. The colour-composite image hasbeen generated on-the-fly from HST images in three differentbands and the spectrum is displayed using SpecView, anapplication plugged-in into the AVO prototype.

Figure 1: The AVO prototype in action.An ESO/WFI image of the GOODS

southern field, overlaid with theHST/ACS data field of view outlines.

The “data-tree” on the left shows theimages available in the Aladin image

server. Data available at selected coor-dinates get highlighted in the tree.

Metadata information is also accessi-ble. The user’s own data can also be

loaded into the prototype. This isbased on the use of IVOA agreed

standards, namely the Data Model,descriptive Metadata, and data inter-

change standards.

and VLT/FORS [spectra], and HST/ACS(optical), XMM and Chandra (X-ray) dataand catalogues. Two cases were dealt with:an extragalactic case on obscured quasars,centred around the Great ObservatoriesOrigin Deep Survey (GOODS) public data,and a Galactic scenario on the classificationof young stellar objects.

The extragalactic case was so successfulthat it turned into the first published scienceresult fully enabled via end-to-end use ofVO tools and systems.

DDISCOVERINGISCOVERING OPTICALLOPTICALLYY FFAINTAINT,,OBSCUREDOBSCURED QUASARSQUASARS

WITHWITH VO VO TOOLSTOOLS

How did we get a scientific paper out of ascience demonstration? The extragalacticscience case revolved around the twoGOODS fields (Giavalisco et al. 2004),namely the Hubble Deep Field-North (HDF-N) and the Chandra Deep Field-South(CDF-S), the most data-rich, deep surveyareas on the sky. Our idea was to use theAVO prototype to look for high-power,supermassive black holes in the centres ofapparently normal looking galaxies.

Black holes lurk at the centres of activegalaxies (AGN) surrounded by dust which isthought to be, on theoretical and observa-tional grounds (see, e.g., Urry & Padovani1995; Jaffe et al. 2004), distributed in a flat-tened configuration, torus-like. When wecan look down the axis of the dust torus andhave a clear view of the black hole and its

surroundings these objects are called “type1” AGN, and display the broad lines andstrong UV emission typical of quasars.“Type 2” AGN, on the other hand, lie withthe dust torus edge-on as viewed from Earthso our view of the black hole is totallyblocked by the dust over a range of wave-lengths from the near-infrared to soft X-rays.

While many dust-obscured low-powerblack holes, the Seyfert 2s, have been iden-tified, until recently few of their high-powercounterparts were known. This was due to asimple selection effect: when the source is alow-power one and therefore, on average,closer to the observer, one can very oftendetect some features related to narrow emis-sion lines on top of the emission from thehost galaxy, which qualify it as a type 2AGN. But when the source is a high-powerone, a so-called QSO 2, and therefore, onaverage, further away from us, the sourcelooks like a normal galaxy.

Our approach was to look for sourceswhere nuclear emission was coming out inthe hard X-ray band, with evidence ofabsorption in the soft band, a signature of anobscured AGN, and the optical flux was veryfaint, a sign of absorption. One key featurewas the use of a correlation discovered byFiore et al. (2003) between the X-ray-to-optical ratio and the X-ray power, whichallowed us to select QSO 2s even when theobjects were so faint that no spectrum, andtherefore no redshift, was available.

We used a large amount of data: deep X-ray (Chandra) and optical (HST/ACS) cata-logues, and identifications, redshifts, andspectra for previously identified sources inthe CDF-S and HDF-N based on VLT andKeck data. Using the AVO prototype made itmuch easier to classify the sources we wereinterested in and to identify the previouslyknown ones, as we could easily integrate allavailable information from images, spectra,and catalogues at once (see Fig. 1 and 2).One interesting feature is the prototype cata-logue cross-matching service, which canaccess all entries in Vizier, at CDS, andallowed us to cross-correlate a variety of cat-alogues very efficiently.

Out of the 546 X-ray sources in theGOODS fields we selected 68 type 2 AGNcandidates, 31 of which qualify as QSO 2(estimated X-ray power > 1044 erg/s; see Fig.3). Our work brings to 40 the number ofQSO 2 in the GOODS fields, an improve-ment of a factor ~4 when compared to theonly nine such sources previously known.These sources are very faint (⟨R ~ 27⟩) andtherefore spectroscopic identification is notpossible for the large majority of objects,even with the largest telescopes currentlyavailable. By using VO methods we aresampling a region of redshift - power spaceso far unreachable with classical methods.For the first time, we can also assess how

many QSO 2 there are down to relativelyfaint X-ray fluxes. We find a surface densitygreater than 330 deg–2 for f(0.5–8keV) ≥ 10–15 erg cm–2 s–1, higher than previ-ously estimated.

The identification of a population ofhigh-power obscured black holes and theactive galaxies in which they live has been akey goal for astronomers and will lead togreater understanding and a refinement ofthe cosmological models describing ourUniverse. The paper reporting these resultshas just been published (Padovani et al.2004).

UUSINGSING THETHE AAVO PVO PROTOTYPEROTOTYPEThe AVO prototype can be downloadedfrom the AVO Web site at http://www.-euro-vo.-org/twiki/bin/view/Avo/SwgDownload. Weencourage astronomers to download the pro-totype, test it, and also use it for their ownresearch. For any problems with the installa-tion and any requests, questions, feedback,and comments you might have please con-tact the AVO team at [email protected].(Please note that this is still a prototype:although some components are prettyrobust, some others are not.)

FFUTUREUTURE DDEVELOPMENTSEVELOPMENTSThe next AVO demonstration event is to beheld in January 2005 and this will see therollout of the first version of the Euro-VOportal, through which the Europeanastronomer will gain secure access to a widerange of data access and manipulation capa-bilities. The science drivers for this nextdemonstration release are being developedby the AVO science team with input fromthe AVO Science Working Group. The AVOPhase-A study is now being completed. TheScience Reference Mission, on which theAVO team is also working, will form the sci-entific basis for the wider scale developmentof the Euro-VO.

AACKNOWLEDGEMENTSCKNOWLEDGEMENTSThe AVO was selected for funding by the FifthFramework Programme of the EuropeanCommunity for research, technological develop-ment and demonstration activities, contract HPRI-CT-2001-50030. We thank the AVO team for theirsuperb work, without which these results couldhave not been obtained, and the many people whohave produced the data on which our paper wasbased, particularly the GOODS, CDF-S, and PennState Teams.

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M., et al. 2004, ApJ, 600, L93 Jaffe, W., Meisenheimer, K., Röttgering, H. J. A.,

et al. 2004, Nature, 429, 47 Padovani, P., Allen, M. G., Rosati, P., & Walton,

N. A. 2004, A&A, 424, 545Szokoly, G. P., Bergeron, J., Hasinger, G., et al.

2004, ApJS, in press [astro-ph/0312324] Urry, C. M., & Padovani, P. 1995, PASP, 107, 803

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Figure 3: Colour-composite images of thehost galaxies of three of the newly founddust-enshrouded supermassive black holes.To the left, images taken with the AdvancedCamera for Surveys on-board the NASA/ESAHubble Space Telescope. To the right theseimages are overlaid with images (in blue)from NASA’s Chandra X-ray Observatory.


IIN PARALLEL with the start of VLToperations in the last quarter of1998, the development of ESO’sresearch facilities in Santiago hasprovided increased opportunities

for students, from ESO member states inparticular, to be trained in Chile under differ-ent ESO programmes.

In this short review, I will essentiallydiscuss students undergoing short-termtraining and students preparing a PhD (ESOstudentship programme) at ESO/Santiago. Iwill show how the number of studentstrained at ESO/Santiago has more than dou-bled since 1999 and discuss the impact ofthe student training programs on the visibil-ity and attractiveness of ESO/Chile.

This analysis is restricted to students inphysics/astrophysics, as the training of stu-dent-engineers and student-technicians,mostly performed at (and for) the observato-ries (LaSilla, Paranal, APEX, ALMA) hasnot been taken into account. Finally, oneshould also mention that student training atESO/Santiago is organized in a way similarto student training at ESO/Garching and allunder the responsibility of the Office forScience.

SSTUDENTSTUDENTS ONONSHORSHORTT--TERMTERM TRAININGTRAINING

This term corresponds in fact to a variety oftraining, with the common characteristic of astay at ESO/Santiago which is less than 6months. Included under this term is researchtraining at the level of Licenciatura orMagistere (2 years before the start of a PhD),of the MSc, DEA/DESS or Laurea gradua-tion (1 year before the start of a PhD), butalso some training performed in the courseof PhD preparation, for example if the stu-dent’s PhD supervisor is collaborating withan ESO/Chile staff member. Therefore, thefunding for the training may come from dif-ferent sources within or outside ESO, suchas the visitors’ programme or the students’home institute (or a mixture). As such, train-ing is in relation with university schedules,mostly taking place during the periodJanuary-August.

Since 1999, the number of students atESO/Santiago has evolved dramatically,demonstrating increasing interest. We hostedin 1999: 5 students; in 2000: 7 students; in2001: 18 students; in 2002: 12 students; in2003: 10 students, and in 2004: 13 students.Over 6 years, 65 students have been trainedat ESO/Santiago, which gives a mean ofaround 11 per year.

Analyzing the university affiliations ofthese 65 students, we observe that 84% ofthe students are registered at a university inan ESO-member state. Breaking down thisfigure per country, we get: 37% in France,18.5% in Italy, 9.5% in Germany, 9.5% inthe Nordic countries and 6.5% in the UK.This distribution is obviously related to theuniversity’s requirements: wheneverresearch training is mandatory during theuniversity course, the students apply ingreater number: this is the case for France,while it does not seem to be as stringent forGermany, Italy or the UK.

Regarding their academic level, abouthalf of the trainees were advanced students(one year before PhD or during PhD).

Regarding the topics of the training, theyreflect the scientific interests of theESO/Chile staff at a given time, and there-fore have been changing with time. Over the6 year period, 26% of the short-term trainingwas in planetary science (including the SolarSystem), 11% about stellar and ISM studies,34% in the field of galaxies and active galac-tic nuclei, 14% in cosmology and 9% in rela-tion with instrumentation and data reductiontechniques.

The training output is frequently a reportwhich the student has to write and defend ather/his university and which is taken intoaccount for the evaluation and award of thedegree. We observe that a good proportionof the students have taken their degree at aranking within the top quartile, demonstrat-ing that ESO/Santiago attracts excellent stu-dents. Moreover, the scientific resultsobtained during the training are often includ-ed in a poster presentation or a refereedpaper published with the ESO/Chile supervi-sor and collaborators.

A large fraction of the short-term stu-dents seem to have appreciated their train-ing. As much as possible, they were giventhe opportunity to visit one of ESO’s obser-vatories in Chile. For all of them, it has beenthe occasion of testing their motivation forresearch and of discovering the reality ofastronomical observations and analysis.Many have confirmed their original choices,and a few changed their mind and decided tomove to other types of activities. This isexactly the goal of training: in all cases,whether research interests have been consol-idated or not, the training has been usefuland has contributed to reducing the gapwhich exists sometimes between dreams andreality. Some of the students on short-term

training later prepared their PhD atESO/Santiago (see below).

In practice, the conditions for a success-ful training are: a strong motivation, curios-ity, adaptability to a new environment, abili-ty to work with some independence and tobe pro-active in the interaction (since theESO/Chile staff spend part of their time atthe observatories and cannot provide a close,day-to-day supervision). Therefore,advanced students are better suited for short-term training at ESO/Santiago. It is also rec-ommended to start contacts with potentialESO/Chile supervisors very early (inNovember/ December) so that a good train-ing-project can be prepared and its fundingput in place.

Information about short-term studenttraining at ESO/Santiago can be found in thewebpage: www.sc.eso.org/santiago/science(check the ESO/Chile Scientific VisitorsProgramme).

SSTUDENTSTUDENTS PREPPREPARINGARINGAA PPHHD D ININ COCO--SUPERSUPERVISIONVISION

This is the ESO studentship programme, ofwhich a detailed description can be found onthe ESO webpage (www.eso.org/gen-fac/adm/pers/vacant/). In brief, ESO pro-vides a two year studentship for studentspreparing their PhD in co-supervision. Thestudent has to be registered in the universitywhere the PhD will be defended, and hastwo co-supervisors: one at ESO/Santiago (orESO/Garching if the student is hosted atESO/Garching) and one in her/his home uni-versity (preferably located in one of the ESOmember states, although this is not mandato-ry). The third year of PhD preparationshould normally be funded by the universityor laboratory of the co-supervisor.Applications for this programme can be sub-mitted once a year, by mid-June. Currently,about 20 PhD students are under this ESOprogramme, half at ESO/Garching and halfat ESO/Santiago. There must be an excellentcoordination between the two co-supervi-sors, for a good definition of the PhD projectand a smooth development of the PhD.

Regarding the PhDs prepared atESO/Santiago, again, there has been anincrease in the number of studentshipoffered since 1999, by almost a factor two.In 1999, there were 6 PhD students at vari-ous stages of their PhD, while as ofSeptember 2004 we have 10 and another onearriving within a few months. Of course thisnumber fluctuates slightly as the students’

SSTUDENTSTUDENTS AATT ESO/SESO/SANTIAGOANTIAGO: : THETHE PERIODPERIOD 1999-20041999-2004

DDANIELLEANIELLE AALLOINLLOIN, , ESO/CHILE OFFICE FOR SCIENCE

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works advance, but a figure of 10 is the base.From 1999 to 2004, there were a total of

26 PhD students at ESO/Santiago: 10 havesuccessfully defended their PhD, and all butone are now postdocs in various observato-ries or laboratories; 6 are planning to defendtheir PhD at the end of 2004 or early 2005; 2will present their PhD around the end of2005; and 6 others are just finishing theirfirst year and therefore will present theirPhD at the end of 2006, while 2 are juststarting.

For this sample of 26 PhD students, 90%of the PhD affiliations are at universities inESO member-states (13 in France, 3 in Italy,3 in Germany, 2 in Belgium, 1 in Swedenand 1 in the UK). The distribution per sub-ject is as follows: 7 PhDs are in the field ofplanetary science, 7 in the field of galaxiesand active galactic nuclei, 7 in cosmology, 3in stellar physics and 2 in relation withinstrumentation or data reduction tech-niques.

Contrary to a classical university envi-

ronment, PhD students at ESO/Santiago donot have many opportunities to attendingdedicated courses on a given subject. Wetried to compensate for this lack of formalcourse work in several ways: most of theinternational astronomical workshops organ-ized in Chile start with a tutorial by a promi-nent speaker specifically targeted for stu-dents, several schools and topical meetingshave been organized and senior visitors whocan bring in their academic experience havebeen invited. As well, Chilean universitiesoffer a variety of excellent astronomy cours-es which PhD students can attend if deemednecessary. The student’s non-ESO co-super-visor is also encouraged to come and spendsome time at ESO/Santiago to appreciate thescientific environment of the student andmake the necessary adjustments. In general,this works quite well.

As a specific feature, PhD students atESO/Santiago have the possibility to takepart in an observatory project (La Silla orParanal) which puts them in close contact

with telescopes, instrumentation and observ-ing procedures. Most students enjoy theobservatory projects during which they gainobservational expertise.

CCONCLUDINGONCLUDING REMARKSREMARKSOver the past 6 years, students’ short-termtraining and PhD preparations atESO/Santiago have become an importantactivity and played a significant role inadvertising ESO facilities. ESO/Chile hasincreased its attractiveness, in particular atthe postdoctoral level (as shown by a steadygrowth in the number and quality of fellow-ship applications for ESO/Chile). The short-term training helps students to test theirmotivation for research. Short-term trainingand PhD preparations contribute to strength-ening links between ESO/Chile staff andastronomers in the ESO member states.They also stimulate in an excellent mannerthe research activities of ESO/Chile staffand give ESO/Santiago its multi-culturalflavour and its youth, our future!

TTHE GOAL of the meeting was todraw some of the best astron-omy researchers from everypart of the world to showcasethe most recent scientific suc-

cesses of the Garching/Munich astronomycommunity, and to also allow the localresearchers to learn from the rest of theworld. The Conference was held at theInstitute for Plasma Physics in Garching,Germany on June 21–25, 2004.

Supermassive black holes (SMBHs) areamong the most spectacular objects in theUniverse, that shed light on fundamentalphysical phenomena occurring in theirimmediate vicinity, such as accretion of gasand strong gravity effects. Historically,theories of accretion have been developedand refined based on observational studies ofindividual SMBHs that are believed to bepowering quasars, first discovered more than40 years ago. This research stood somewhatseparate from cosmology that deals primari-ly with the formation and evolution of galax-ies. However, in recent years, it has beenestablished that black holes lie in the centresof practically all galaxies, and significantlinks between cosmic structure formationand evolution and supermassive black holeshave been demonstrated. Nowadays, SMBHare not just interesting laboratories of exoticphysics, but have direct impact on the evolu-tion of the Universe as we see it: they are animportant ingredient of cosmological models.

The meeting brought together about 170scientists from the extra-galactic astronomy,cosmology and accretion physics communi-ties to discuss the implications of the connec-tion between supermassive black holegrowth and galaxy formation. For the firsttime in a meeting of this series, a video-con-ference connection was established betweenthe Conference hall and both MPA and ESO,to allow the local students to listen to someof the most interesting talks.

We started on Monday with a welcomeaddress from Rashid Sunyaev (MPA), andcontinued with a session dedicated to theobservations of supermassive black holes inthe local Universe. Topical reviews weregiven by Ralf Bender (MPE/USM), who dis-cussed the fundamental correlationsobserved between SMBHs and their hostgalactic bulges, and Guineviere Kauffmann(MPA), who presented the analysis of theimpressive amount of data on local AGNgathered by the Sloan Digital Sky Survey(SDSS). They both pointed out the importantfact that only relatively small mass blackholes are actively accreting (and growing)today, while many hints suggest that thebiggest black holes in the Universe wereformed at very high redshift.

The second session was devoted to theobservations of SMBH in the distant uni-verse. Xiaohui Fan (Arizona) and Niel Brand(Penn State) presented the optical and X-rayviews, respectively, of the most distant QSOs

known. They have vividly illustrated thegreat progress being made in this area thanksto the SDSS and the Chandra and XMM-Newton X-ray satellites. The first day endedwith a few talks, including a review byBernhard Brandl (Leiden), on the first scien-tific results in the field from the SpitzerSpace Telescope, launched into space inAugust 2003.

One of the most important open ques-tions in the field is whether black holes wereseeds or by-products of galaxy formation.The second day of the meeting was entirelydevoted to the theory of black hole formationand growth in the early Universe. The morn-ing session started with a review by MartinRees (Cambridge) on the physical processthrough which the first black holes mighthave formed, while Piero Madau (U ofCalifornia Observatories) and Abraham Loeb(Harvard) discussed in more detail what pre-dictions can be made by incorporating thephysics and dynamics of growing black holesinto standard Cold Dark Matter Cosmo-logical models. Also, state-of-the-art cosmo-logical numerical simulations were presentedat the meeting: Volker Bromm (Harvard)concentrated on simulating the process offormation of the first stars and black holes,while Volker Springel and Tiziana Di Matteo(MPA) showed spectacular simulations ofevolving and interacting galaxies with super-massive black holes in their centres. Finally,Zoltan Haiman (Columbia University) dis-

Report on the joint MPReport on the joint MPA/MPE/ESO/USM workshop on A/MPE/ESO/USM workshop on

GGROWINGROWING BBLACKLACK HHOLESOLES: A: ACCRETIONCCRETION ININ AA

CCOSMOLOGICALOSMOLOGICAL CCONTEXTONTEXT

AANDREANDREA MMERLONIERLONI ANDAND SSERGEIERGEI NNAAYYAKSHINAKSHIN (MPA-GARCHING)


cussed the role of accreting black holes inthe re-ionization of the Universe.

The day, started under a chilly rain,ended with a sunny ‘Beer and Brez’n’ partyin the MPE/MPA garden. Faithful to theBavarian spirit, the organizers provided theguests with more than 250 liters of locallybrewed beer!

The following morning the centre ofattention was the centre of our own galaxy:the SMBH also known as Sgr A*. ReinhardGenzel (MPA), Mark Morris (UCLA) andFred Baganoff (MIT) presented the amazingnew data gathered in the last few years withthe biggest telescopes on earth (VLT, Keck)as well as in space (Chandra). Thanks tothese efforts, the case for a black hole in theGalactic Centre appears now to be iron-clad.Moreover, future theoretical interpretationof the data will likely significantly improveour understanding of the black hole growthmechanisms and the associated star forma-tion very close to the black hole.

Another important question was dis-cussed on Wednesday afternoon: the role ofgalaxy mergers, accretion and stellar cap-tures for the overall black hole growth.David Merritt (Rochester) reviewed the var-ious mechanisms by which SMBHs induceobservable changes in the distribution ofluminous and dark matter at the centres ofgalaxies. Later in the afternoon, MarekAbramowicz (Chalmers University) sug-

gested that there are no theoretical limits onthe rate at which the gas can be swallowedby a black hole.

On Thursday morning a new window ofthe gravito-electro-magnetic spectrum wasopened to the study of SMBHs: gravitation-al waves. Sterl Phinney (Caltech) gave acomprehensive overview of the excitingprospects and challenges that lie ahead forgravitational wave astronomy. BernardSchutz (MPI-Potsdam) illustrated thebreathtakingly complex numerical simula-tions of BH-BH merger events, a possibletarget of the upcoming Laser InterferometerSpace Antenna (LISA). And an overview ofthe technical aspects of the LISA missionwas given by Karsten Danzmann (AEIHannover).

How important is the feedback fromsupermassive black holes in structure forma-tion? This fundamental question was deeplyinvestigated by many of the speakers ofThursday afternoon’s session. Andrew King(Leicester) advocated the importance ofpowerful outflows from rapidly accretingblack holes in establishing the observedlinks between SMBHs and host galaxies.Mitchell Begelman (Colorado) showed howAGN feedback can solve the mystery of thelack of strong cooling flows in the centres ofmany clusters of galaxies, and WilliamForman (Harvard) presented many newChandra observations of hot gas in galaxyclusters.

A chance to relax during this intenseconference was the conference dinner at theAugustiner Grossgaststaetten in centralMunich. The local organizing committee,Jorge Cuadra, Andrea Merloni, EmmiMeyer, Sergei Nayakshin and RashidSunyaev, all MPA, Thibaut Paumard (MPE)and Gijs Verdoes Kleijn (ESO), presentedsome gifts to the MPA secretaries (MariaDepner, Gabi Kratschmann, Kate O’Sheaand Cornelia Rickl), whose help throughoutthe organization of the conference and dur-ing it was a real blessing to the LOC.

On the last day of the meeting, the clas-sical problem of what the X-ray Backgroundtells us about AGN activity and obscuration,both at low and at high redshifts, was revis-ited in the light of the most recent resultsfrom deep X-ray surveys by Andy Fabian(Cambridge) and Guenther Hasinger (MPE),and from the multi-waveband GOODS sur-vey by Meg Urry (Yale University). Themeeting was closed in an optimistic andsomewhat humorous way by the ‘BlackHole Manifesto’ of Roger Blandford(Caltech), in which some of the most inter-esting developments from the meeting weresummarized.

Those interested in more details of themeeting are invited to visit http://www.MPA-Garching.MPG.DE/~bh-grow/. Conference pro-ceedings are to be published by SpringerVerlag as a part of the “ESO AstrophysicsSymposia” series.

Report on a brainstorming meeting about theReport on a brainstorming meeting about the

ALMA IALMA INTERDISCIPLINARNTERDISCIPLINARYY TTEACHINGEACHING PPROJECTROJECT

HHENRIENRI BBOFFINOFFIN ANDAND RRICHARDICHARD WWESTEST (ESO)

RRECENT large-scale surveyshave documented a wide-spread lack of interest in sci-ence and technology amongEurope’s young people. This

development is highly worrying as it maylead to a lack of qualified scientists andteachers and may ultimately have dramaticdemographic consequences on this conti-nent. Various reasons for this situation havebeen identified and it is generally acknowl-edged that teaching quality at the primaryand secondary levels plays a crucial role inthis context. Means and methods to remedythis undesirable situation are being lookedinto in many countries and the EuropeanCommission has issued a strong plea for thecreation of new educational initiatives, inparticular broad and general ones that areeasily adaptable to national curricula.

Having conducted educational pro-grammes at the European level since 1993,the Education and Public RelationsDepartment (EPR) of the European SouthernObservatory has recently embarked upon

another ambitious teaching project, this timein connection with the ongoing, interconti-nental ALMA programme that aims at theinstallation of a unique astrophysicalresearch facility consisting of 64 12-m radioantennas at 5000m altitude in the ChileanAtacama desert by 2011. The related front-line science and technology, as well theunusual site, clearly have a great potentialfor interdisciplinary education.

A first presentation of ideas for anALMA educational project took place dur-ing the large-scale “Physics on Stage 3” edu-cational meeting/fair at ESA/ESTEC inNoordwijk (The Netherlands) in November2003. For this, Bernhard Mackowiak (ESOEPR) had produced a first draft text on somesubjects that may be included in a future“ALMA Teachers’ Cookbook”. A direct out-come was the creation of a small group ofexpert teachers from secondary schools inseveral European countries, who expressedinterest in contributing to the developmentof ALMA-related educational material forinterdisciplinary teaching.

A first exchange of views with the mem-bers of this group took place in December2003. Following the extensive and time-con-suming preparations for the Venus Transitevent in June 2004, the ESO EPRDepartment is now promoting a new interna-tional pilot educational project referred asthe ALMA-Interdisciplinary TeachingProject (ALMA-ITP). The main goal is todevelop and produce ALMA-related educa-tional material at the secondary level, in par-ticular a comprehensive ALMA Guide forInterdisciplinary Teaching. This project isfully in line with the current trend of lower-ing the walls between the various subjectsand moving towards more interdisciplinaryteaching in Europe’s secondary schools. Itconstitutes a contribution towards allevia-tion of the current educational crisis, byattempting to provide attractive opportuni-ties for more real-life, project-oriented edu-cation to teachers and their students. At thesame time, it is obvious that the materialmay also form a very useful basis for similarefforts in other countries involved in the

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ALMA programme, following suitableadaptation to the national and regional cur-ricula. For this, the ALMA IntegratedProject Team (IPT) on Outreach andEducation will act as a clearing house.

As a next step in this process, we inviteda small number of expert teachers, many ofwhom participated in last year’s ALMA-presentation during Physics on Stage 3 andalso a number of scientists to come togetherduring a one-day brainstorming meeting atthe ESO-HQ in Garching. It started with anoverview of the ALMA programme present-ed by H. Boffin (ESO), co-leader of theALMA IPT. As well as illustrating theimportance of millimetric and sub-millimet-ric astronomy for the study of some of themost relevant astrophysical fields of the 21stcentury, the talk also tried to answer thequestion “why is ALMA what it is and whyis it located at Chajnantor?” It was followedby an overview by R. West (ESO) on futureESO projects and their potential role foreducation. A series of more specialised talkswere then delivered: on the geography of theregion (B. Mackowiak, ESO), on geologyand the effect of Plate Tectonics on the for-mation of the Andes (E. Scheuber, Instituteof Geological Sciences, Free UniversityBerlin, Germany), on the fauna and flora ofthe Atacama desert (M. Grenon, GenevaObservatory, Switzerland), and on the med-ical aspects of living and working at highaltitude (H. Welsch, German Air ForceInstitute of Aviation Medicine, Königsbrück,Germany).

These talks clearly illustrated the uniqueand highly exciting potential of the ALMA

programme for education in variousdomains. This should come as no surprise,however: ALMA will be located on one ofthe highest plateaus in the world at a altitudeof more than 5000m. As Ekkehard Scheuberpointed out, Chajnantor is surrounded byvolcanoes, one of which still active (Lascar),and also by ignimbrite outcrops with largecalderas, some of which are potentiallyexplosive as they overlay large quantities ofgas. The Atacama Desert is by all means themost arid place on Earth with an annual pre-cipitation of less than 10 mm. By compari-son, the Sahara desert receives 20 mm ofwater per year and Death Valley inCalifornia no less than 120 mm a year! Butas Michel Grenon also showed with a uniqueand beautiful set of pictures obtained duringnumerous trips to this region during the pastthree decades, the Atacama Desert is farfrom being a place without life. Nature has –as always – shown wonderful creativity toexplore many ways to circumvent theextreme UV-exposure, the dramatic lack ofwater as well as the enormous temperaturevariations, e.g., by having plants growinginto the ground instead of out of it. And hehad found plants at an altitude of 5150m,that is, even higher than the ALMA site!

The important medical aspects of livingand working at high altitude were wellexposed by German Air Force medical spe-cialist Heiko Welsch who discussed thephysiological mechanisms behind mountainsickness and how the lack of oxygen at highaltitude can lead to hypoxia and sometimesincur life-threatening situations where quickaction is paramount. Nobody should think

that this added circumstance of the ALMAprogramme may be taken easily and themedical service must be well planned andalways ready.

After this first series of talks, H. Wilson(ESA Education Office) presented the ESAEducational Kit on the International SpaceStation (ISS) and the lessons learned frompreparing an interdisciplinary teaching kit ata European level. She stressed the greatimportance of involving experienced teach-ers from the start and to have a thoroughreview of a prototype teaching kit before thefinal release. Christiane Henkel and Denisvan de Wetering (University of Bielefeld,Germany) presented a research project oninterdisciplinary teaching and the impor-tance of stating right from the beginning theobjectives of the project as well as the targetaudience. They also reminded the partici-pants of one of the goals of interdisciplinaryteaching: to teach students core skills whichare needed in our modern, accelerated andcommunicative society. These are, theyassert, flexibility, creativity, cooperation andcommunication ability, teamwork ability,and tolerance, all keys for learning andworking with others.

Two additional talks, both very muchappreciated by all the participants, weregiven via a videoconference link from theESO Santiago office, by Daniel Hofstadt(ESO) and Jörg Eschwey (ESO). DanielHofstadt shared his deep knowledge of theAtacama culture with its centuries-old tradi-tions and the uniqueness of the sceneryaround San Pedro de Atacama. He also pre-

H.

Hey

er (E

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Expert teachers and scientists from all over Europe attended the first ALMA-ITP meeting at ESO HQ in Garching (Sept. 4, 2004).


sented the various environment impact stud-ies which were done prior the start of theALMA project. These covered cultural,anthropological, archaeological and biologi-cal aspects. Jörg Eschwey embarked theaudience on a trip from Antofagasta to theChajnantor ALMA site to illustrate the com-plex logistics necessary to build major infra-structures in such extreme conditions. Heexplained the numerous challenges to besolved to construct a 12m wide road thatallows the transport of 100 ton antennas, ona variety of soils between 2700m to 5000maltitude and the need to take into accountand protect the different biotopes along theroute. One example concerned the safety ofa local species of rats, named tuco-tuco, byconstructing tunnels under the road to allowthe animals to transit it without trouble. Allthis has to be done while chasing large num-bers of very curious donkeys watching theprogress of the roadwork.

With all this information in hand torealise the enormous potential of ALMA-related education, the meeting participantsembarked upon a wide-ranging discussion.It was clear from the beginning that theexperience of interdisciplinary teaching isvery different from country to country. Itwas therefore quickly realised that any mate-rial to be produced must be in modular formand be easily adaptable to the curricula ofindividual countries. The need to translatethe material into as many different lan-guages as possible was obvious, addinganother complex element to this project.

The participants expressed a lot ofenthusiasm and are eager to start the devel-opment and realisation of the project.During the discussion, a list of about 30 spe-cific topics that could be addressed in amodular way was drawn up, serving as auseful starting point. Many of the teachersvolunteered to work on them, with the goalto circulate drafts of the individual modulesin some months' time. Specific conclusionswere drawn about the desirable format of thefuture ALMA educational toolkit and on itsfoci. It will be concerned with the extraordi-nary and unique science to be made usingthe ALMA observatory and the variety ofchallenges to build an observatory likeALMA at Chajnantor. As one participantstated, this is really about “how to makefrontier science in extreme conditions”. Theprimary target audience is students in sec-ondary schools, i.e. 11–18 years old.

A first draft of the ALMA Interdisciplin-ary Teaching Project should become avail-able early 2005. It will then be evaluated andtested by teachers after which improvementswill be made in a next iteration. It is plannedto have a useful version ready for distribu-tion via existing networks by the end of thesummer of next year.

Obituary

JJÜRGENÜRGEN SSTOCKTOCK1923 – 20041923 – 2004

On April 19, 2004 Jürgen Stock passed away at the age of 80. Jürgen Stock wasnever on the payroll of ESO, but he had tremendous impact on the early years of theorganisation. In 1951 Stock did his PhD in Hamburg - his supervisor was OttoHeckmann, who later became the first Director General of ESO. After some years inCleveland - and with a one year interval at Boyden Observatory, South Africa - Stockwas asked by Gerard Kuiper to do a site test in Chile. The University of Chicago lookedfor a mountain in the Santiago area to put up a 1.5-m-telescope in the southern hemi-sphere. Stock accepted and took off for Chile within days. The trip, that was supposedto last a few weeks, lasted more than three years. "As a result, the world's largest col-lection of astronomical instruments is now in Chile", recalled Jürgen Stock four decadeslater.

After his arrival in Chile, Stock realised immediately, that the three pre-selectedmountains close to Santiago were not really suited for an observatory. He decided to dosite tests much further north, in the area of La Serena with its unique climate conditionsbetween the cold Pacific Ocean and the high mountains. Stock travelled to Vicuña andclimbed a nearby mountain on foot. At some distance he spotted a mountain with a per-fect topography - quite isolated with an almost flat top. As the mountain was 40 km offthe next accessible road, he organised mules and horses and made a trip to the top a fewmonths later. He remembered it vividly: "The first night was so impressive: a perfectlyclear night, absolutely calm, with a comfortable temperature: It couldn't be better. Ontop of that, it was perfectly dark in all directions." In those times an unknown mountainsomewhere in Chile, this mountain has now a magnificent name: Cerro Tololo.

Due to Stock’s euphoric reports from Chile, the project was handed over fromUniversity of Chicago to AURA. Now, the astronomers thought of something much big-ger than just a site for a 1.5-m-telescope. With sufficient funds, Stock set up severalteams for extensive site testing activities in that area. He checked almost a dozen moun-tains - Stock spent nearly three years on horse back to climb many mountains. While hewas on expedition, he made notes every day - including not only the atmospheric con-ditions and astronomical observations but also the everyday life: Stock mentioned prob-lems with the mules, the progress in the construction of some shelter on the mountains,the need for a support team bringing food and water, the conduct of the local people andso on. Each time he was back in Vicuña, he sent a letter with those notes to his bossDonald Shane at Lick Observatory. In a stroke of genius, Shane decided to type thereports, copy and distribute them among the astronomers in the US. Due to that, the"Stock reports" survived until today. The reports should be read by everyone who wish-es to get an idea of what it meant to conquer the Andes for astronomy - there is a copyin the ESO historic archives.

In 1962, Tololo was finally chosen and Stock became the founding director of thatobservatory. In fact, he did almost everything: He was involved in the road construc-tion, the blasting, the construction of the domes and support buildings etc. Due to hispersonal contact with Otto Heckmann and Jan Oort, Stock kept the Europeans informedabout the progress in Chile. ESO - at that time about to sign the contracts with SouthAfrica - decided to establish their observatory in Chile. Without this personal contactbetween Heckmann and Stock, ESO's first observatory might well have been erected inSouth Africa.

At first, there was a plan to build the American and the European observatories onthe same mountain. But ESO soon decided to keep its independence and to build anobservatory on La Silla. A wise decision, but Jan Oort realised the problems connectedwith that. He wrote in a letter to Heckmann in late 1963: "The worst thing is that weneed some extra time to check the quality of the mountain and to construct a road to thetop - and we should always keep in mind that we don't have a Dr. Stock."

In the 1960s, both Stock and Heckmann were directors of major observatories. In1970 Stock was forced to leave Chile. He went to Venezuela and founded the CIDAobservatory in the Andes near Mérida. His achievements for astronomy in Chile havealmost been forgotten. Those of us who had the privilege to know him will rememberhis fine sense of humour, his brilliant mind and his great heart. Jürgen Stock was a manof great vision - modern astronomy has lost one of its last pioneers.

DIRK H. LORENZENHAMBURG, GERMANY

SSCIENCE reigned supreme in Stockholm for a period of four daysin late August this year, as some 1800 scientists, administra-tors, policy-makers and media representatives from 68 coun-

tries convened at the EUROSCIENCE Open Forum, the first pan-European inter- and transdisciplinary science meeting on ourContinent.

The purpose of the meeting was to ‘provide an interdisciplinaryforum for open dialogue, debate and discussion on science and tech-nology in society’. With such an ambitious goal, a new meeting for-mat to enforce the interdisciplinarity, and a fairly heterogeneous tar-get audience, the participants clearly realized the experimental natureof this undertaking.

Nonetheless, with 270 speakers from 33 countries and more than80 scientific workshops, symposia, plenary lectures and debates, itwas clearly anything but a modest beginning. Further to this, exhibi-tion stands at the Conference Centre, an impressive public outreachprogramme, including numerous events and happenings, e.g. in thenearby King’s Gardens, completed the programme.

As reported in the last issue of the Messenger, ESO took anactive part in the meeting, together with its EIROforum partners. Theactivities included a 3-hour session on some of the scientific activi-ties within the EIROforum organizations, a very successful outreachevent with videoconferences between some of our facilities andSwedish schoolchildren and a major exhibition stand.

Given the experimental character of the event, how did it fare?Firstly, with a wide offer of parallel sessions, participants may

have had a hard time choosing what to attend. Secondly, some scien-tists may have found the interdisciplinary aspect unusual.Nonetheless, as the meeting got underway, the overwhelmingimpression was that the idea had caught on and the format becameaccepted.

Many science policy makers and administrators used the oppor-tunity to deepen their understanding of individual fields of sciencewhile at the same time discussing a wide variety of policy-relatedissues. These sessions were very well attended.

But the idea of the ‘Open Forum’ was clearly to further the dia-logue between science and society. For this reason, it was particular-

ly pleasing to notethe strong mediainterest. Some 350journalists (60from Sweden)attended the meet-ing, which featureda series of dedicat-ed press briefings.One of the firstpress briefingsdealt with the pos-sible discovery of arocky exoplanet, as

announced by ESO on 25 August (cf ESO Press Release 22/04‘Fourteen Times the Earth - ESO HARPS Instrument DiscoversSmallest Ever Extra-Solar Planet’). The media coverage, both of thisparticular announcement and of the many other topics discussed dur-ing the meeting was highly gratifying, conquering the front pages ofrenowned broadsheet newspapers such as the Financial Times and,on occasions, rivalling the coverage of the ongoing 2004 OlympicGames in Athens.

The next EUROSCIENCE Open Forum will take place inMunich, between 15-19 July 2006. It is hoped that many more scien-tists will wish to attend this meeting supporting a much increased andneeded interaction between scientists, the media and the public.

All photos: Jennifer Hay (EFDA-JET/EIROforum)

The Messenger 11766

RREPOREPORTT ONON THETHE

EEUROUROSSCIENCECIENCE OOPENPEN FFORUMORUM 20042004CCLAUSLAUS MMADSENADSEN, ESO

The ESOF 2004 venue: The Stocholm City ConferenceCentre, Folkets Hus, and ‘Norra Latin’.

The launch of the EIROforum Science TeachersInitiative, now embedded in the NUCLEUS programme,was announced at the EIROforum stand. Speaking tothe media is Russ Hodge from the EMBL.

Moderated by Richard West from ESO, the Outreach session gave schoolchildren fromStockholm an opportunity to talk directly with scientists at the EIROforum organisa-tions. From Paranal, Nancy Ageorges presented the VLT and took numerous questions.Seen here is Wojciech Fundamenski from the JET fusion reactor in Culham.


PPIERREIERRE KKERERVELLAVELLA

DURING the five years that I spent at ESO, inGarching and then in Chile, it seems to methat I lived several lives altogether. The firstone was that of an international student, as Ileft Paris to start my thesis at ESOHeadquarters in Garching. I still rememberthe first time I arrived in Munich, with just asingle suitcase, checking carefully that I wastaking the right U-Bahn and bus to reachESO. Of course, all the German languagethat I learnt in school had vanished com-pletely from my mind... The VLTI team atthis time was quite small, with only fivemembers, while it is now a solid group ofmore than 20 staff. Overall, my installationwent well, and I soon began my work onwhat was to become VINCI, the test instru-ment for the VLTI. Over the course of myPh.D., I took an active part in the construc-tion of this instrument, from the blank pageup to its installation and operation atParanal. In between, I had the great privilegeto see the first fringes of the VLTI with thetest siderostats (March 2001) and then withthe Unit Telescopes (October 2001) in thecontrol seat of the interferometer.

After the defenceof my thesis, a secondlife started in early2002, when I moved toChile to take up dutiesat Paranal in the VLTIteam. Living in Chileis a very pleasingexperience, thanks in

particular to the kindness of the Chilean peo-ple and the beauty of the landscapes. Untilthe MIDI instrument started operations in2004, VINCI got more time than initiallyforeseen to observe the wonderful Paranalsky. It was eventually operated for almostthree years. The large quantity of publiccommissioning data and their good qualityallowed me to conduct a number of interest-ing research projects, among which severalmade their way to ESO Press Releases (αCentauri, Achernar,…). Today, I feel that my300 nights at Paranal were very well spenttime! I left Chile and ESO in February 2004,to take up a permanent position at ParisObservatory in France. Working for ESOwas a rich and fulfilling experience that Iwarmly recommend to any astronomer, bothfrom the professional and personal point ofviews!

CCARLOSARLOS DDEE BBREUCKREUCK

MY INTEREST in

Astronomy started

very early by

browsing books in

the local library.

After finishing high

school in Belgium, I

decided to study

Astronomy at the

University of Leiden. Moving to a country

with different culinary standards/traditions

wasn't always easy, but I have found it a very

rewarding experience to get to know other

places, and to work in an international envi-

ronment such as ESO. After my undergradu-

ate studies, I continued as a PhD-student in

Leiden to search for the most distant radio

galaxies using new all-sky radio surveys.

After a few months, I moved for 3 years to

Livermore, California, which gave me

access to the new Keck telescopes. Just

before returning to Leiden we found what

we were looking for: the most distant known

radio galaxy at z=5.2.

After obtaining my PhD in 2000, I

became a Marie Curie Fellow at the IAP in

Paris. Spoiled by using large telescopes, I

started several observing programs on the

VLT. I also expanded my horizons into mm-

astronomy to observe the CO gas and dust in

the high redshift radio galaxies found during

my thesis. With the development of ALMA,

the ESO Fellowship was a logical next step

in my career. Since I arrived in Garching in

September 2003, I have spent most of my

time on research, but I have also used the

opportunities to get to know ESO better. In

particular, I have helped organizing the

Journal Club, which is only one of the many

weekly talks happening on the ESO-MPA-

MPE campus. I am also involved in the sci-

entific preparation of ALMA, which will

soon become an important tool in my

research. Recently, we have set up the

European ALMA newsletter to inform the

European millimetric community about the

construction of ALMA.

FFELLOWSELLOWS AATT ESOESOCCELINEELINE PPEROUXEROUX

A FEW YEARS back,I crossed theBritish Channelone way in orderto spend my nightsgazing at a starrysky as part ofu n d e r g r a d u a t eprojects. Aftercompleting my PhD at the University ofCambridge in 2001, I worked in Italy beforejoining ESO in late 2003.

I am curious to understand the globalproperties of galaxies over large time scales.Rather than studying the light they emit,which fades at large distances, my approachconsists of decoding the imprints thatgaseous structures leave in the spectrum of abackground quasar. These “quasarabsorbers” provide a measure of both theneutral gas and metallicity content of theUniverse back to early cosmic times. Mywork, in particular, suggests that a sub-classof the quasar absorbers, named sub-DampedLyman-alpha systems, are major contribu-tors to the observable baryonic content athigh-redshift. I have used ESO archive datato build a sample of these systems in order tomeasure the global metallicity in the neutralgas phase. I am now able to extend this workto higher redshifts thanks to a new set ofVLT data. Quasar absorbers are indeedextremely powerful observational tools but,paradoxically, they are also mysterious andtheir relation to emitting galaxies stillremains to be clearly established.

As part of my contribution to the organ-isation, I am involved in making thepipeline-reduced UVES science framesavailable to the community. In parallel, I amsupporting the X-shooter project, the first ofthe second generation of VLT instruments.The way new ideas and global astrophysicalissues are debated with both locals and visi-tors makes ESO a very unique place to me.The only problem is that the way the build-ing is laid out means I still have troublesfinding my office coming back from thebathroom...

The Messenger 11768

WWith VST and OmegaCam nearing completion itbecame urgent to define new procedures for themost efficient exploitation of these survey facil-ities, also in view of the VISTA infrared surveytelescope expected to join the Paranal

Observatory in 2007. Moreover, even before VISTA, the UKIDSSproject (Warren 2002) will provide the ESO community with majorinfrared surveys that may be in need of an extensive optical counter-part.

The issue was extensively discussed at the dedicated ESOWorkshop on “Large Programmes and Public Surveys” that was heldin Garching in May, 2003 (see Wagner & Leibundgut 2004, for asummary of the Workshop). A set of guidelines emerged from thediscussion which are worth summarizing here again.

Public Imaging Surveys ought to be conducted with the widestdirect involvement of the community and should comply with thefollowing guidelines:

• Ensure scientific excellence, enabling competitive research byESO community on frontier scientific areas;

• Provide a continuous supply of scientific targets for the instru-ment complement of the VLT/VLTI;

• Ensure that the set of implemented surveys covers the main sci-entific areas being actively investigated by the ESO community;

• Ensure the optimization of each survey for both primary andother possible scientific exploitations of the same data set;

• Ensure a balanced distribution of survey targets over rightascension, so as to avoid scheduling congestion at the survey tele-scopes and at the VLT/VLTI;

• Ensure optical/near-IR coverage of sky areas covered by com-plementary ground and/or space facilities at other wavelengths andwhich data are publicly accessible to the ESO community;

• Ensure coordination between optical and near-infrared surveys.To properly match UKIDSS and VISTA surveys it is anticipated thatVST will have to dedicate to large surveys a fraction of its total timecomparable to that dedicated by VISTA (75%, according to theESO/UK Agreement).

On the basis of previous experience, it was expected that severalsurveys will have to be implemented in parallel, so as to explore avariety of depth, area, multi-band, and galactic latitude combina-tions, while avoiding excessive concentrations at specific rightascensions.

It was soon recognized that the normal procedure for ESO pro-posals (with teams in the community directly submitting proposalsfor OPC evaluation) could not ensure the scientific and schedulingcoordination that is indispensable for a most efficient utilization ofthe telescopes. An intermediate step was then envisaged in order toensure that any given survey could serve the broadest possible rangeof scientific applications, that a proper balance is maintained amongthe various scientific areas, and that the resulting set of surveys is dis-tributed as uniformly as possible in right ascension.

Following these guidelines ESO submitted to the STC a docu-ment describing the new “Procedures for Public Surveys”. The doc-ument was then discussed in depth by a Working Group jointlyappointed by STC and OPC. The final document was approved bythe STC in April 2004, and is reproduced fully below.

It was also recognized that the completion of a survey and thetimely delivery of its science grade products (co-added, mosaicedand photometrically and astrometrically calibrated images, catalogs,etc.) is a major undertaking, especially in terms of human resources.It appeared that a team would be more likely to embark in such an

effort for the benefit of the community, if there was a clear perspec-tive of scientific follow up at the VLT/VLTI. As a result, the new pro-cedures foresee that a team proposing itself for carrying out a surveycan also submit to OPC a proposal for the scientific follow-up at theVLT/VLTI, which will be evaluated jointly with the survey proposal.Such a procedure will both help motivating the team, and ensuringthat the survey products comply with their scientific specifications.

Before proceeding to appoint the Public Survey Panel (PSP),ESO issued on September 15 a call for "Letters of Intent" for publicsurvey proposals. Teams intending to submit such proposals will beasked to provide a succinct description of the survey, including itsscientific objectives and a brief description of the observations. Withthis information in hand ESO will then proceed to appoint the PSPmembers, making sure that the PSP scientific expertise will matchthe whole range of astronomical applications of the surveys to beproposed.

RREFERENCESEFERENCESWagner, S., & Leibundgut, B. 2004, ESO Messenger, 115, 41Warren, S. 2002, ESO Messenger, 108, 31

PPROCEDURESROCEDURES FORFOR ESO PESO PUBLICUBLIC SSURURVEYSVEYS

APublic Survey is understood to be an observing programmein which the investigators commit to produce and make pub-licly available, within a defined time, a fully reduced and sci-

entifically usable data set that is likely to be of general use to a broad-er community of astronomers. The practical implementation ofPublic Imaging Surveys will proceed as follows.

1. ESO will periodically issue a “Call for Public Imaging SurveyProposals”, for groups in the community to propose Public ImagingSurveys. Proposals shall include a scientific rationale, observingstrategy, estimated observing time, and its distribution over observ-ing Periods, as well as a detailed description of the responsibilitiesthe team would be ready to take in case of approval of the proposedsurvey.

2. ESO will ask INAF (for the VST Consortium) and theOmegaCam Consortium to provide detailed descriptions for theobserving programmes they intend to conduct in their guaranteedtime (GTO) at the VST over the first 4 semesters. A similar procedurewill be repeated every two years until the completion of the GTOtime.

3. ESO will establish a Public Survey Panel (PSP) including sci-entists expert in a broad range of current astronomical research, withparticular emphasis on those areas that can profit from PublicSurveys. The PSP prime mandate will be to review the Public SurveyProposals and, taking into account the GTO programmes, elaborate ascientifically and observationally well coordinated set of PublicSurveys. This process may well imply merging different proposals,or expanding their aims beyond the original ones e.g., in the filter set,depth, area, coordinates, etc. In order to achieve these goals the PSPwill involve representatives from both the GTO teams and selectedteams having submitted Survey Proposals. On the basis of theachieved coordination the selected survey teams will modify the sur-vey proposals, describing the scientific rationale, observational strat-egy, and data product specifications (e.g. photometric and astromet-ric accuracy, images, catalogs, delivery time, etc.) as agreed in thecourse of these activities.

4. The PSP will review these modified proposals and forwardthem to the OPC along with a document illustrating the criteriaadopted for the optimization and coordination of the recommended

A NA NEWEW SSTTARARTT FORFOR PPUBLICUBLIC SSURURVEYSVEYSAALLVIOVIO RRENZINIENZINI (ESO)

Ann

ounc

emen

ts


set of surveys, and the motivations for hav-ing rejected others.

5. These resulting proposals for PublicSurvey may include proposals for subse-quent proprietary observations with otherESO facilities which are designed to exploitthe results of the survey in question. TheOPC will then provide simultaneous recom-mendations on the time to allocate both tothe survey and to its followup. AManagement Plan for each survey will alsobe attached to the proposal for ESO review.

6. For each approved Public SurveyESO will negotiate with the PI the extent ofESO support that could be given, and thetimeline of product delivery. The allocationof observing time for the scientific follow upof the survey will be subject to the timelydelivery of the survey products and theircompliance to the specifications.

7. The PSP Document, the final propos-als for Public Surveys and the description ofthe GTO programmes will be made avail-able on the web prior to the regular Call forProposals for the VST.

8. Proposals for Proprietary Surveys canbe submitted as usual following the regularCalls for Proposals, thus ensuring that theOPC evaluates all survey proposals (publicand proprietary).

9. The ESO/ST-ECF Science ArchiveFacility (SAF) will be the collection pointfor the survey products and the primarypoint of publication/availability of theseproducts to the ESO community. ESO willassist the survey teams to define and pack-age their data products in a manner consis-tent with SAF and Virtual Observatory stan-dards and will integrate the products into theSAF.

10. Survey programs that directly com-plement other public surveys should them-selves be carried out as Public Surveys. Incase of GTO programs in this category, ESOwill encourage the GTO Teams making theirsurvey products public and to submit pro-posals for the scientific follow up at otherESO telescopes, following the same proce-dures outlined in item 5 above. In all casesthe allocation of the OPC recommendedobserving time for the scientific follow upwill be subject to the timely delivery of thesurvey products and their compliance to thespecifications.

11. The PSP will periodically review theprogress of the surveys and will assess thecompliance to the specification of the surveyproducts. The PSP will then forward to ESODirectorate its recommendations concerningthe continuation of each survey and the allo-cation of the associated follow-up time atother facilities.

(1 June 2004 - 31 (1 June 2004 - 31 August 2004)August 2004)

ARRIVARRIVALSALSEUROPE

BIANCHINI, Andrea (I) StudentKHRISTOFOROVA, Maria (RU) StudentKORNWEIBEL, Nicholas (UK) Software EngineerMARTEAU, Stephane (F) Oper.support Scient.MARTINEZ, Pascal (F) Paid AssociateMÜLLER, Michael (D) Mechanical EngineerPATT, Ferdinand (D) EngineerPOPESSO, Paola (I) Paid AssociateRETZLAFF, Jörg (D) Paid AssociateSOENKE, Christian (D) Software EngineerTAIT, Donald (UK) Project PlannerVERNET, Joel (F) Fellow

CHILE

DUMKE, Michael (D) Paid AssociateHUNTER, Ian (UK) StudentMASON, Elena (I) Op.staff AstronomerPANTIN, Eric (F) Paid AssociateRAGAINI, Silvia (I) StudentSTEFANON, Mauro (I) Paid Associate

DEPDEPARARTURESTURESEUROPE

AHMADIA, Aron (US) StudentANTONIUCCI, Simone (I) StudentBERTA, Stefano (I) StudentDIETL, Ottomar (D) Maint. TechnicianDI FOLCO, Emmanuel (F) StudentGRILLO, Claudio (D) StudentHAU, George (UK) FellowKURZ, Richard (US) Chief EngineerSNEL, Ralph (NL) Paid AssociateSURDEJ, Isabelle (B) StudentVUCHOT, Luc (F) StudentWEGERER, Stefan (D) Mechanics TechnicianWEIDINGER, Michael (DK) Student

CHILE

CARVAJAL, Alfredo (CL) Procurement OfficerCLARKE, Fraser (UK) FellowDELVA, Pacome (F) StudentDISSEAU, Ludovic (F) StudentGERMANY, Lisa (AUS) FellowGIUFFRIDA, Giuliano (I) StudentHAUBOIS, Xavier (F) StudentILLANES, Esteban (CL) Public Relations OfficerMEDVES, Giuseppe (I) Paid AssociateMILLOT, Nadia (F) StudentNOTERDAEME, Pasquier (B) StudentPEREZ, Juan Pablo (CL) Electronic EngineerVAISANEN, Petri (FI) Fellow

PERSONNELPERSONNEL MOVEMENTSMOVEMENTS

Applications are invited for the position of a

DDESKTOPESKTOP PPUBLISHINGUBLISHING/G/GRAPHICSRAPHICS SSPECIALISTPECIALISTCAREER PATH: III

Assignment: Within the ESO Education and Public Relations Department team, her/his main tasks will comprise:• Layout and complete pre-press preparation of ESO publications (Quarterly journal, Annual Report, brochures, posters, etc.)• Interaction with printers• Preparing multimedia/web presentations• Assisting in keeping the ESO EPR website up to date• Assisting in the preparation of scientific illustrations

Qualification and experience: Diploma in Graphic Arts (or equivalent), at least 3 years of experience in a relevant profession-al environment. She/he must be proficient in standard software packages for:

• DTP (print and electronic media) (Quark Xpress/In-Design)• Photoshop, Illustrator• Macromedia Director/Flash or equivalent• GoLive/Dreamweaver (or equivalent)/knowledge of HTML

Experience in scientific animations (e.g. morphing, etc.) would be an advantage. She/he must be fluent in English. German atworking level would be an advantage.

Duty Station: Garching near Munich, Germany.

Starting date: As soon as possible.

Remuneration and Contract: We offer an attractive remuneration package including a competitive salary (tax free), compre-hensive pension scheme and medical, educational and other social benefits as well as financial help in relocating your family.The initial contract is for a period of three years with the possibility of a fixed-term extension or permanence. The title or grademay be subject to change according to qualification and the number of years of experience.

Applications: If you are interested in working in a stimulating international research environment and in areas of frontline sci-ence and technology, please send us your CV (in English) and the ESO Application Form by

25 October 2004

All applications should include the names of four individuals willing to give professional references and preferably samples ofwork.

For further information please contact Mrs. Barbara Ounnas. You are also strongly encouraged to consult the ESO Home Page(http://www.eso.org) for additional information about ESO.

The Messenger 11770

ESO WESO Workshop Prorkshop Proceedings Still Aoceedings Still AvailablevailableMany ESO Conference and Workshop Proceedings are still available and may be ordered at the European Southern Observatory. Some ofthe more recent ones are listed below.

No. Title Price

54 Topical Meeting on “Adaptive Optics”, October 2–6, 1995, Garching, Germany. M. Cullum (ed.) € 40.–

55 NICMOS and the VLT. A New Era of High Resolution Near Infrared Imaging and Spectroscopy.

Pula, Sardinia, Italy, May 26–27, 1998 € 10.–

56 ESO/OSA Topical Meeting on “Astronomy with Adaptive Optics – Present Results and Future Programs”. Sonthofen, Germany, September 7–11, 1999. D. Bonaccini (ed.) € 50.–

57 Bäckaskog Workshop on “Extremely Large Telescopes”. Bäckaskog, Sweden, June 1–2, 1999. T. Andersen, A. Ardeberg, R. Gilmozzi (eds.) € 30.–

58 Beyond Conventional Adaptive Optics, Venice, Italy, May 7–10, 2001. E. Vernet, R. Ragazzoni, S. Esposito, N. Hubin (eds.) € 50.–


ESO FESO FELLOWSHIPELLOWSHIP PPROGRAMMEROGRAMME 2004/20052004/2005The European Southern Observatory awards several postdoctoral fellowships to provide young scientists opportunities andfacilities to enhance their research programmes. Its goal is to bring them into close contact with the instruments, activities,and people at one of the world’s foremost observatories. For more information about ESO’s astronomical research activitiesplease consult http://www.eso.org/science/.Fellows have ample opportunities for scientific collaborations: a list of the ESO staff and fellows, and their research interestcan be found at http://www.eso.org/science/sci-pers.html and http://www.sc.eso.org/santiago/science/person.html. The ESO Headquarters inMunich, Germany host the Space Telescope European Coordinating Facility and are situated in the immediate neighbourhoodof the Max-Planck-Institutes for Astrophysics and for Extraterrestrial Physics and are only a few kilometers away from theObservatory of the Ludwig-Maximilian University. In Chile, fellows have the opportunity to collaborate with the rapidlyexpanding Chilean astronomical community in a growing partnership between ESO and the host country’s academic com-munity. In Garching, fellows spend beside their personal research up to 25% of their time on support or development activities oftheir choice in the area of e.g. instrumentation, user support, archive, VLTI, ALMA, public relations or science operations atthe Paranal Observatory. Fellowships in Garching start with an initial contract of one year followed by a two-year extension. In Chile, the fellowships are granted for one year initially with an extension of three additional years. During the first threeyears, the fellows are assigned to either the Paranal or La Silla operations groups. Together with the astronomer in charge,they contribute to the operations at a level of 80 nights per year up on the mountain and 35 days per year at the SantiagoOffice. During the fourth year there is no functional work and several options are provided. The fellow may be hosted by aChilean institution and will thus be eligible to apply for Chilean observing time on all telescopes in Chile. The other optionsare to spend the fourth year either at ESO’s Astronomy Center in Santiago, Chile, or the ESO Headquarters in Garching, orany institute of astronomy/astrophysics in an ESO member state.

We offer an attractive remuneration package including a competitive salary (tax-free), comprehensive social benefits, and pro-vide financial support in relocating families. Furthermore, an expatriation allowance as well as some other allowances maybe added. The Outline of the Terms of Service for Fellows provides some more details on employment conditions/benefits.Candidates will be notified of the results of the selection process in December 2004/January 2005. Fellowships beginbetween April and October of the year in which they are awarded. Selected fellows can join ESO only after having complet-ed their doctorate. The closing date for applications is October 15, 2004.

Please apply by:- filling the form available at http://www.eso.org/gen-fac/adm/pers/forms/fellow04-form.pdf attaching to your application: a CurriculumVitae including a publication list (the latter split into refereed and non-refereed articles, please) an outline of your current andpast research, as well as of your research plans if you came to ESO (max. 2 pages) a brief outline of your technical/observa-tional experience (max. 1 page) - arranging for three letters of reference from persons familiar with your scientific work to be sent to ESO before the applica-tion deadline.

All documents should be typed and in English. The application material has to be addressed to:European Southern ObservatoryFellowship ProgrammeKarl-Schwarzschild-Str. 285748 Garching bei [email protected]

Contact persons: Nathalie Kastelyn, Tel. +49 89 320 06-217, Fax +49 89 320 06-497, e-mail: [email protected] for applications for ChileKatjuscha Haase, Tel. +49 89 320 06-219, Fax +49 89 320 06-497, e-mail: [email protected] for applications for Garching

All material must reach ESO by the deadline (October 15); the same applies to recommendation letters which should be sentdirectly by the reference person; applications arriving after the deadline or incomplete applications will not be considered!

ESO, the European Southern Observa-tory, was created in 1962 to “... establishand operate an astronomical observatoryin the southern hemisphere, equippedwith powerful instruments, with the aim offurthering and organising collaborationin astronomy...” It is supported by elevencountries: Belgium, Denmark, Finland,France, Germany, Italy, the Netherlands,Portugal, Sweden, Switzerland and theUnited Kingdom. ESO operates at threesites in the Atacama desert region ofChile. The Very Large Telescope (VLT), islocated on Paranal, a 2,600 m high moun-tain approximately 130 km south of Anto-fagasta. The VLT consists of four 8.2metre diameter telescopes. These tele-scopes can be used separately, or incombination as a giant interferometer(VLTI). At La Silla, 600 km north ofSantiago de Chile at 2,400 m altitude,ESO operates several optical telescopeswith diameters up to 3.6 m. The third siteis the 5,000 m high Llano de Chajnantor,near San Pedro de Atacama. Here a newsubmillimetre telescope (APEX) is beingcompleted, and a large submillimetre-wave array of 64 antennas (ALMA) isunder development. Over 1300 proposalsare made each year for the use of theESO telescopes. The ESO headquartersare located in Garching, near Munich,Germany. This is the scientific, technicaland administrative centre of ESO wheretechnical development programmes arecarried out to provide the Paranal and LaSilla observatories with the mostadvanced instruments. ESO employsabout 320 international staff members,Fellows and Associates in Europe andChile, and about 160 local staff membersin Chile.

The ESO MESSENGER is published fourtimes a year: normally in March, June,September and December. ESO alsopublishes Conference Proceedings, Pre-prints, Technical Notes and other materi-al connected to its activities. PressReleases inform the media about particu-lar events. For further information, con-tact the ESO Education and PublicRelations Department at the followingaddress:

EUROPEAN SOUTHERN OBSERVATORYKarl-Schwarzschild-Str. 2 D-85748 Garching bei München Germany Tel. (089) 320 06-0 Telefax (089) 3202362Email: [email protected]: http://www.eso.org

The ESO Messenger:Editor: Peter ShaverTechnical editor: Henri Boffinhttp://www.eso.org/messenger/

Printed by Universitätsdruckerei WOLF & SOHNHeidemannstr. 166D-80939 MünchenGermany

ISSN 0722-6691

CCONTENTSONTENTS

C. CESARSKY – ESO Welcomes Finland as Eleventh Member State . . . . . . . . . . . . . . . . . . . . 2K. MATTILA ET AL. – Astronomy in Finland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3ESO PRESS RELEASE 23/04 – Is this Speck of Light an Exoplanet? . . . . . . . . . . . . . . . . . . . . .11

TTELESCOPESELESCOPES ANDAND IINSTRUMENTNSTRUMENTAATIONTIONP.O. LAGAGE ET AL. – Successful Commissioning of VISIR: the Mid-Infrared VLT Instrument .12H. BONNET ET AL. – First Light of SINFONI at the VLT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17R. ARSENAULT ET AL. – Third MACAO-VLTI Curvature AO System Now Installed . . . . . . . . . . .25J.P. EMERSON ET AL. – VISTA: The Visible & Infrared Survey Telescope for Astronomy . . . . . . .27T. WILSON – ALMA News . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32L. GERMANY – News From La Silla . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32C. IZZO ET AL. – Gasgano & ESO VIMOS Pipeline released . . . . . . . . . . . . . . . . . . . . . . . . . . . .33ESO PRESS PHOTO 27/04 – The Milky Way above La Silla . . . . . . . . . . . . . . . . . . . . . . . . . . .35

RREPOREPORTSTS FROMFROM OOBSERBSERVERSVERSR. CHINI ET AL. – The Birth of a Massive Star............................................................................36N. CHRISTLIEB, D. REIMERS & L. WISOTZKI – The Stellar Content of the

Hamburg/ESO Survey ...................................................................................40C. CACCIARI, A. BRAGAGLIA & E. CARRETTA – Flames Spectroscopy of RGB stars

in the Globular Cluster NGC 2808 ................................................................47L. PASQUINI ET AL. – VLT Observations of Beryllium in a Globular Cluster ...............................50P. KERVELLA ET AL. – Cepheid Pulsations Resolved by the VLTI................................................53P. PADOVANI ET AL. – First Science for the Virtual Observatory .................................................58

OOTHERTHER AASTRONOMICALSTRONOMICAL NNEWSEWSD. ALLOIN – Students at ESO/Santiago: The Period 1999-2004...............................................61A. MERLONI & S. NAYAKSHIN – Report on the joint MPA/MPE/ESO/USM Workshop

on « Growing Black Holes: Accretion in a Cosmological Context » ............62H. BOFFIN & R. WEST – Report on a Brainstorming Meeting about the

« ALMA Interdisciplinary Teaching Project » .................................................63D.H. LORENZEN – Obituary: Jürgen Stock 1923–2004...............................................................65C. MADSEN – Report on the EuroScience Open Forum 2004 ...................................................66Fellows at ESO – C. De Breuck, P. Kervella, C. Peroux............................................................67

AANNOUNCEMENTSNNOUNCEMENTSA. RENZINI – A New Start for Public Surveys.............................................................................68Personnel Movements...............................................................................................................69Vacancy: Desktop Publishing/Graphics Specialist ...................................................................70ESO Fellowship Programme .....................................................................................................71

Front Cover Picture: The Birth of a Massive Star

Three-colour ISAAC mosaic of the star forming region M 17. The field size is about 7 u 7 arc minutes, theeffective spatial resolution is about 0.6 arc seconds; wavelength coding: blue 1.25 µm, green 1.65 µm, red2.2 µm. See the article by R. Chini et al. on page 36.

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