Galaxies and cosmology: the Galaxies and cosmology: the promise of ALMApromise of ALMA

Andrew Blain Andrew Blain

CaltechCaltech

1414thth May 2004 May 2004

ALMA North American Workshop

ContentsContents

CMB and SZ – cosmology aspectCMB and SZ – cosmology aspect

Examples of what we know ALMA can seeExamples of what we know ALMA can see– Sub-arcsec resolution Sub-arcsec resolution – microJy sensitivitiesmicroJy sensitivities– No confusion noiseNo confusion noise– Continuum and line surveysContinuum and line surveys

Advances over all existing/proposed capabilitiesAdvances over all existing/proposed capabilities– Sensitivity is not infinite!Sensitivity is not infinite!– Relatively small field of viewRelatively small field of view

Fine angular scale CMB and SZFine angular scale CMB and SZALMA (with compact array) will be ALMA (with compact array) will be extremely sensitive to arcmin-scale extremely sensitive to arcmin-scale CMB power, from clusters, filaments CMB power, from clusters, filaments and primordial fluctuationsand primordial fluctuations

Carlstrom et al.Arcmin resolution

Fine resolution will reveal features in the intracluster medium to resolve physical

conditions in cluster gas

ALMA

X-ray

SZ effect

Chandra – low-z Hydra cluster with substructure

Example target: the AntennaeExample target: the Antennae

Excellent example of distinct Excellent example of distinct opt/UV and IR luminosityopt/UV and IR luminosity

Interaction long known, Interaction long known, but great luminosity but great luminosity unexpected unexpected – ~90% energy escapes ~90% energy escapes

at far-IR wavelengths at far-IR wavelengths

Resolved images Resolved images important important – Relevant scales Relevant scales

~1” at high ~1” at high redshiftredshift

HST WFPC2

ISOCAM

CSO/SHARC-2Dowell et al.

Observed far-IR/submm SEDsObserved far-IR/submm SEDsNon-thermal Non-thermal radioradio

Thermal dustThermal dust– Dominates Dominates

luminosity luminosity – Hotter in AGN?Hotter in AGN?– See SpitzerSee Spitzer

Molecular and Molecular and atomic linesatomic lines– Mm CO / HCNMm CO / HCN

– IR: C/N/O/HIR: C/N/O/H22

– IR: C=C PAHIR: C=C PAH

Submm population: backgroundsSubmm population: backgrounds

Many sources of dataMany sources of dataTotal far-IR and optical Total far-IR and optical background intensity background intensity comparablecomparableMost of submm Most of submm background detected by background detected by SCUBASCUBA

Backgrounds yield Backgrounds yield weaker constraints on weaker constraints on evolution than countsevolution than counts

SCUB

A

ISO

Model: BJSLKI ‘ Models: BJSLKI 99SC

UBA

ALMA will resolve the most distant ALMA will resolve the most distant galaxies down to L*galaxies down to L*

Example objects known from existing Example objects known from existing ground based observationsground based observations– High-redshift continuum emission High-redshift continuum emission – Marginally resolved CO spectra reveal internal Marginally resolved CO spectra reveal internal

structure, and dynamical massesstructure, and dynamical masses– Spitzer will reveal a huge sample to follow upSpitzer will reveal a huge sample to follow up

Redshifts are ‘moderate’ z~2-3Redshifts are ‘moderate’ z~2-3– ALMA will see CO structure in detailALMA will see CO structure in detail– ALMA will probe fainter, still unconfusedALMA will probe fainter, still unconfused

Example Deep Submm Example Deep Submm ImageImage

Abell 1835Abell 1835– Hale 3-color opticalHale 3-color optical– 850-micron SCUBA850-micron SCUBA

Contrast:Contrast:– Image resolutionImage resolution– Visible populationsVisible populations– Orthogonal submm and Orthogonal submm and

optical viewsoptical views

One of 7 images from One of 7 images from Smail et al. SCUBA lens Smail et al. SCUBA lens survey (97-02)survey (97-02)– About 25 SCUBA cluster About 25 SCUBA cluster

imagesimagesIvison et al. (2000) 2.5’ square

Example IDed submm galaxyExample IDed submm galaxy

Unusually bright exampleUnusually bright exampleMay not see most important region in the opticalMay not see most important region in the opticalJ2 is a Lyman-break galaxy (Adelberger & Steidel 2000)J2 is a Lyman-break galaxy (Adelberger & Steidel 2000)J1 is a cluster member post-starburst (Tecza et al. 2004)J1 is a cluster member post-starburst (Tecza et al. 2004)J1n is an Extremely Red Object (ERO; Ivison 2001)J1n is an Extremely Red Object (ERO; Ivison 2001)– Remains red in deeper Keck-NIRC dataRemains red in deeper Keck-NIRC data

Both J1n & J2 are at z = 2.55 – radio and mm from J1nBoth J1n & J2 are at z = 2.55 – radio and mm from J1n

Ivison et al (2000, 2001)

High-redshift COHigh-redshift CO

K band image (8” square), with IRAM CO contours of an ultraluminous galaxy at z=3.35

Genzel et al. (2004)

Abell 2218 ISO 15µmµm and optical image (2.5’ across); Metcalf et al. Orange – left imageRed – bottom image

SAFIR field SAFIR field exceeds extent exceeds extent of the ISO of the ISO image, yet has image, yet has spatial spatial resolution as resolution as good as the good as the inteferometer, inteferometer, plus spectral plus spectral information information

Upper: submm continuum; lower optical HST

|

|

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Note: submm, optical and mid-IR show

different populations

40” square

Abell 851

Submm galaxies in CO(3-2),(4-3)Submm galaxies in CO(3-2),(4-3)

Neri et al. ApJ (2003); IRAM interferometer; source of detections given on individual frames8 more now have CO measurements

Frayer et al. N4 Smail et al. N2.4Chapman et al.

Population of submm galaxiesPopulation of submm galaxies

Most data is at 850 Most data is at 850 µµmm– New bright limit from Barnard New bright limit from Barnard

et alet al– Very few are Galactic Very few are Galactic

contaminating cloudscontaminating clouds

First limit was at 2.8 mm First limit was at 2.8 mm (BIMA)(BIMA)Also bright 95/175 Also bright 95/175 µµm counts m counts (ISO), that will be dramatically (ISO), that will be dramatically improved by Spitzerimproved by SpitzerAlso data at 1.2mm (MAMBO); Also data at 1.2mm (MAMBO); 1.1mm (BOLOCAM) and 1.1mm (BOLOCAM) and 450450µmµm

Blain et al (2002)updated

Orange stars – Barnard et al (2004) 850-µm upper limit

***

Unique submm access to highest zUnique submm access to highest z

Redshift the steep Redshift the steep submm SEDsubmm SEDCounteracts inverse Counteracts inverse square law dimmingsquare law dimmingDetect high-z galaxies as Detect high-z galaxies as easily as those at z=0easily as those at z=0– Low-z galaxies do not Low-z galaxies do not

dominate submm imagesdominate submm images– Unique high-z access in Unique high-z access in

mm and submmmm and submm

Ultimate limit is CMB Ultimate limit is CMB heatingheating

Existing limits to informationExisting limits to information

Limited few arcsec positional accuracy from Limited few arcsec positional accuracy from 10-m class submm telescopes 10-m class submm telescopes – challenges accurate identification and makes it challenges accurate identification and makes it

difficult to target for spectroscopydifficult to target for spectroscopy– So far VLA radio positions required for spectroscopySo far VLA radio positions required for spectroscopy

Optical spectroscopy has provided redshifts for Optical spectroscopy has provided redshifts for more of this population that might have been more of this population that might have been expected (Chapman et al 2003; 2004)expected (Chapman et al 2003; 2004)

ALMA will ALMA will notnot be limited in this way be limited in this way– To only cooler, more luminous, lower redshift systemsTo only cooler, more luminous, lower redshift systems

850-850-µm µm redshift distributionredshift distribution

Histogram: sample Histogram: sample expanded from Nature listexpanded from Nature listExpected submm & radio Expected submm & radio redshift distributions from redshift distributions from Scott Chapman’s modelScott Chapman’s model– Consistent with studeis of Consistent with studeis of

star-formation history that star-formation history that show far-IR domiates show far-IR domiates optical at z~2, but result optical at z~2, but result now now MUCHMUCH more robust more robust

z~1.5 gap is the z~1.5 gap is the ‘spectroscopic desert’‘spectroscopic desert’Bias against highest z is Bias against highest z is likely modest, but still likely modest, but still uncertainuncertainChapman et al. (2003; Nature; 2004; ApJ subm.)

Signs of large-scale structureSigns of large-scale structure

HDF-N/GOODS field submm/radio HDF-N/GOODS field submm/radio spectroscopic survey (Chapman et al spectroscopic survey (Chapman et al 2004)2004)

Geometry is extreme pencil beam Geometry is extreme pencil beam – 5 x 3000 Mpc5 x 3000 Mpc– Same for ALMA Same for ALMA

Circles: all galaxies with redshiftsCircles: all galaxies with redshifts– Empty: z knownEmpty: z known– Colored: z in ‘associations’ within Colored: z in ‘associations’ within

1200 km/s1200 km/s

Note more ‘associations’ than expected Note more ‘associations’ than expected unless powerful galaxy-galaxy correlationunless powerful galaxy-galaxy correlation– rr00 ~ 7 ~ 7hh-1-1 MpcMpc

ALMA will resolve less luminous ALMA will resolve less luminous associated structure and map the regions associated structure and map the regions in detail in detail

Blain et al. (astro-ph/0405035)

ALMA’s resolution puts it aheadALMA’s resolution puts it ahead

Resolution is very fine, both to avoid confusion Resolution is very fine, both to avoid confusion from overlapping sources, and resolve their from overlapping sources, and resolve their internal structureinternal structureThe second absolutely demands ALMAThe second absolutely demands ALMAThe first can also be achieved by large aperture The first can also be achieved by large aperture single-antenna telescopes on the ground and in single-antenna telescopes on the ground and in spacespaceThese can provide wide-field finder imagesThese can provide wide-field finder images25-m submm ‘Atacama Telescope’ Cornell-25-m submm ‘Atacama Telescope’ Cornell-Caltech studyCaltech study

Confusion noiseConfusion noise

Model based on Model based on SCUBA/ISO SCUBA/ISO populationspopulationsFlux for 1 source per Flux for 1 source per beam ~ RMS noisebeam ~ RMS noiseExtragalactic sources Extragalactic sources dominate for small dominate for small aperturesapertures– When < 500When < 500µm ~25-µm ~25-

m aperture very m aperture very importantimportant

– <0.1mJy sure to find <0.1mJy sure to find submm counterparts submm counterparts to high-z optical to high-z optical galaxiesgalaxies

Time to reach confusion limitTime to reach confusion limit

Galactic & extragalactic Galactic & extragalactic confusion limitsconfusion limits– Sensitivity Sensitivity αα D D-1-1

Practical limit ~10-100hr Practical limit ~10-100hr in any fieldin any field

At shortest wavelengths At shortest wavelengths need large aperture to need large aperture to allow deep surveysallow deep surveys

Note speed at 850Note speed at 850µmµm– 9” resolution 9” resolution

Confusion is avoided with ALMAConfusion is avoided with ALMA

Current missions in blackCurrent missions in black– Spitzer is +\Spitzer is +\

Green bar is just a 500m Green bar is just a 500m baseline baseline ALMAALMARed bar is 10-m Red bar is 10-m SAFIRSAFIR– Confusion from galaxies Confusion from galaxies

not met for many minutes not met for many minutes or hoursor hours

– At shortest wavelengths At shortest wavelengths very deep observations are very deep observations are possiblepossible

Factor of 10 in resolution Factor of 10 in resolution over existing facilities is over existing facilities is very powerfulvery powerful

▬▬

Submm observations of galaxies Submm observations of galaxies mature in ALMA eramature in ALMA era

Resolution to match HST/JWST and resolve Resolution to match HST/JWST and resolve internal structure of high-z galaxiesinternal structure of high-z galaxies3-D spectral information of even the most 3-D spectral information of even the most obscured regions obscured regions – Reveals astrophysics at work Reveals astrophysics at work – Provides direct redshiftsProvides direct redshifts– ALMA astrophysical probes are self containedALMA astrophysical probes are self contained

New populations of objects, and pre-reionization New populations of objects, and pre-reionization galaxies galaxies – HH22 lines / first metals – dust and fine-structure lines lines / first metals – dust and fine-structure lines

‘‘Photometric redshifts’Photometric redshifts’

Combine different bands to Combine different bands to estimate T & z togetherestimate T & z together– No strong far-IR spectral No strong far-IR spectral

breaks or featuresbreaks or features

Strongest lever from 200-Strongest lever from 200-600600µmµm– Based on knowledge of Based on knowledge of

galaxies/site, can galaxies/site, can probably design 2 optimal probably design 2 optimal bands bands

Once z known, get Once z known, get accurate luminosityaccurate luminosityALMA can do this, but ALMA can do this, but combined with real redshift combined with real redshift information from spectrainformation from spectra

SMGs’ SEDs: FIR-radio assumedSMGs’ SEDs: FIR-radio assumed

Blain, Barnard & Chapman 2003; Blain et al (2004; astro-ph/0404438)

Solid circles: newSubmm sources

Radio loud caveat above ~60KSquares: low-z, Dunne et al.

Empty circles: moderate z,mainly Stanford et al.

Crosses: variety of known redshifts(vertical = lensed)

Solid circles: Chapman SMGs

Lines: low-z trends

Scatter in T by >~40%

ALMA can explore new region here

ALMA can explore new region here

Line emissionLine emission

Optical spectroscopy will probably never be able to keep Optical spectroscopy will probably never be able to keep up with mid-IR discoveriesup with mid-IR discoveries– Especially the ‘hard cases’, deeply enshrouded in dust at z>5Especially the ‘hard cases’, deeply enshrouded in dust at z>5

Far-IR emission lines and CO rotational emission reveal Far-IR emission lines and CO rotational emission reveal astrophysics of gas involved in star formationastrophysics of gas involved in star formation– Heterodyne R>10Heterodyne R>1066 and 8-GHz bandwidth: ALMA can see details and 8-GHz bandwidth: ALMA can see details– ALMA can make spatially & spectrally resolved images of the ALMA can make spatially & spectrally resolved images of the

most interesting galaxies found in <1hrmost interesting galaxies found in <1hr

Little information on far-IR lines available so far Little information on far-IR lines available so far – SOFIA will test this scienceSOFIA will test this science– Spitzer covers restframe spectra of low-redshift galaxiesSpitzer covers restframe spectra of low-redshift galaxies– CII and OI pair can give redshifts for z~4.5; CO may be CII and OI pair can give redshifts for z~4.5; CO may be

exhausted / not excited / not present at these redshiftsexhausted / not excited / not present at these redshifts– High redshift AGN & LBGs show metallicities are high early on High redshift AGN & LBGs show metallicities are high early on

Lines available for detectionLines available for detection

Left: 870Left: 870µm window; 5x10µm window; 5x10-21-21 Wm Wm-2-2 (10- (10-σσ 18 min) 18 min)Right: 350µm window; 4-10x10Right: 350µm window; 4-10x10-20-20 Wm Wm-2-2 (10- (10-σσ 8.7 hr) 8.7 hr)

Long wavelength – in blind searches detect ~ 1 hour Long wavelength – in blind searches detect ~ 1 hour -1-1

– ALMA is fastest planned instrument working at longer wavelengthsALMA is fastest planned instrument working at longer wavelengths

Gives Gives resolvedresolved spectroscopy – redshift and dynamical information spectroscopy – redshift and dynamical information

Summary Summary

ALMA will detect huge numbers of galaxies, ALMA will detect huge numbers of galaxies, deeper than any other facilitydeeper than any other facilityProbe astrophysics Probe astrophysics – during most active phase at z~2-3during most active phase at z~2-3– Prior to re-ionizationPrior to re-ionization

Resolved spectral images will reveal masses Resolved spectral images will reveal masses and mass assembly of galaxiesand mass assembly of galaxiesDRSM shows demand will be highDRSM shows demand will be highAll areas of extragalactic astrophysics will All areas of extragalactic astrophysics will benefit from ALMAbenefit from ALMA