11

INFRARED PROPERTIESINFRARED PROPERTIES

OF STAR FORMING DWARF GALAXIESOF STAR FORMING DWARF GALAXIES

Ovidiu VaduvescuOvidiu VaduvescuPostdoc, UKZN & SAAO, South AfricaPostdoc, UKZN & SAAO, South Africa

My Canadian PhDMy Canadian PhDSep 2000 – Nov 2005Sep 2000 – Nov 2005

Defended on Defended on 18 Nov18 Nov 2005 2005York University, Toronto, Ontario CanadaYork University, Toronto, Ontario Canada

Presented on July 17th, 2006Presented on July 17th, 2006ESO, Vitacura, ChileESO, Vitacura, Chile

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What is a dwarf galaxy?What is a dwarf galaxy?

Any galaxy MAny galaxy MBB>-16 (Tamman 1994) or M>-16 (Tamman 1994) or MVV>-18 (Grebel >-18 (Grebel 2000); 2000);

Three to five types of dwarf galaxies: Three to five types of dwarf galaxies:

Dwarf Irregulars (dIs); Dwarf Irregulars (dIs); Blue Compact Dwarfs (BCDs); Blue Compact Dwarfs (BCDs);

Dwarf Ellipticals (dEs) / Dwarf Spheroidals (dSphs); Dwarf Ellipticals (dEs) / Dwarf Spheroidals (dSphs); Dwarf Spirals (dS’s)? Dwarf Spirals (dS’s)?

Any evolutionary relations? Any evolutionary relations?

dIs – BCDs – dEs ?dIs – BCDs – dEs ? Dwarfs – Giants ?Dwarfs – Giants ?

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Why star forming dwarf galaxies? Why star forming dwarf galaxies?

They trace the early stages of galaxy evolution; They trace the early stages of galaxy evolution; There is no agreement yet about the evolutionary There is no agreement yet about the evolutionary

connection between dIs, BCDs and dEs; connection between dIs, BCDs and dEs; The closed box model can be checked against the three; The closed box model can be checked against the three; From about 450 galaxies in the Local Volume (< 10 Mpc), From about 450 galaxies in the Local Volume (< 10 Mpc),

there are about 380 dwarfs (85%); there are about 380 dwarfs (85%);

Why prefer the near infrared (NIR)? Why prefer the near infrared (NIR)?

Need a better gauge of mass via the old stellar population; Need a better gauge of mass via the old stellar population; The extinction is very low (about 10x lower than in visible);The extinction is very low (about 10x lower than in visible); Prefer J and KPrefer J and Kss versus H; versus H;

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Three major requirements: Three major requirements:

Deeper NIR imaging (Deeper NIR imaging (KK 23 mag/arcsec 23 mag/arcsec22); );

Accurate distances (Cepheids, TRGB); Accurate distances (Cepheids, TRGB); Precise abundances ([OIII] Precise abundances ([OIII] 4363 line); 4363 line);

Observing samples – 90 dwarfs! Observing samples – 90 dwarfs!

43 dIs in the Local Volume: 43 dIs in the Local Volume: 34 observed by us;34 observed by us; 9 from 2MASS (larger & brighter). 9 from 2MASS (larger & brighter).

16 BCDs in the Virgo Cluster by us; 16 BCDs in the Virgo Cluster by us;

31 dEs from Virgo Cluster and Local Group: 31 dEs from Virgo Cluster and Local Group: 22 in Virgo 22 in Virgo from GOLDMinefrom GOLDMine; ; 9 in the Local Group, from the literature. 9 in the Local Group, from the literature.

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Seven observing runs: Seven observing runs:

CFHT, Hawaii CFHT, Hawaii Direct Imaging (2 runs): Direct Imaging (2 runs): 2002 (3 nights); 2002 (3 nights); 2004 (3 nights). 2004 (3 nights).

29 dIs in the LV; 29 dIs in the LV;

CFHT Presenting… CFHT Presenting…

WARNING:WARNING:

Any unauthorized Any unauthorized interpretation of this interpretation of this picture strictly picture strictly prohibited! prohibited!

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Seven observing runs (continued): Seven observing runs (continued):

OAN-SPM 2.1m, Mexico OAN-SPM 2.1m, Mexico

Direct Imaging (21 nights): Direct Imaging (21 nights):

2001 (4 nights); 2001 (4 nights); 2002 (4 nights); 2002 (4 nights); 2003 (7 nights); 2003 (7 nights); 2004 (6 nights); 2004 (6 nights);

16 BCDs in Virgo; 16 BCDs in Virgo; 6 dIs in the LV; 6 dIs in the LV;

Special thanks to Dr. Michael Richer! Special thanks to Dr. Michael Richer!

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Seven observing runs (continued): Seven observing runs (continued):

Gemini-North, HawaiiGemini-North, Hawaii 2003 (one night). 2003 (one night).

Spectroscopy of Spectroscopy of

4 BCDs in Virgo; 4 BCDs in Virgo;

The Crux besides Gemini North… courtesy of my Nikon The Crux besides Gemini North… courtesy of my Nikon

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Strategies for NIR observing and reduction: Strategies for NIR observing and reduction:

In NIR, the “background noise” comes from: In NIR, the “background noise” comes from:

The atmosphere (airglow); The atmosphere (airglow); The structure (telescope, dome, etc); The structure (telescope, dome, etc); The camera (detector, filters, etc). The camera (detector, filters, etc).

Two components: Two components:

The background level (median of a sky frame); The background level (median of a sky frame); The background pattern (structure, sky frame – next sky The background pattern (structure, sky frame – next sky

frame )frame )

We studied the rate of change of the two in We studied the rate of change of the two in

(Vaduvescu & McCall, PASP 116, 2004)(Vaduvescu & McCall, PASP 116, 2004)

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How often to sample the How often to sample the sky? sky?

Observing sequences:

sky-gal-sky-…-sky-gal-sky

sky-gal-gal-sky- …sky-gal-gal-gal-sky-…etc

Markarian 20910 galaxy frames combined using:

(a) - 10 sky frames(b) - 6 sky frames(c) - 4 sky frames(d) - 2 sky frames

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Conclusions to the background problem: Conclusions to the background problem:

Background level (associated with the airglow); Background level (associated with the airglow); Background pattern (associated with the instrument – Background pattern (associated with the instrument –

movie).

To do 1% surface photometry: To do 1% surface photometry:

Exposures in J must be separated by less than 90 sec;Exposures in J must be separated by less than 90 sec; Exposures in K’ must be separated by less than 120 Exposures in K’ must be separated by less than 120

sec;sec; Use sky–gal–sky–gal–sky– … –sky–gal–sky sequence. Use sky–gal–sky–gal–sky– … –sky–gal–sky sequence.

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Surface photometry of dIs – KILLALL at work! Surface photometry of dIs – KILLALL at work!

KILLALL (Buta & McCall, 1999) – kill ~10,000 stars in five KILLALL (Buta & McCall, 1999) – kill ~10,000 stars in five steps

(a) K(a) Kss image of NGC 1569; (b) Unresolved component, after image of NGC 1569; (b) Unresolved component, after KILLALLKILLALL

Resolved/Total flux ratios less than 5% in KResolved/Total flux ratios less than 5% in Kss and 10% in J and 10% in J

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Surface photometry of dIsSurface photometry of dIs

Exponential, de Vaucouleurs, and Sersic laws do not fit Exponential, de Vaucouleurs, and Sersic laws do not fit dIs. dIs.

Sech law does: I = ISech law does: I = Ioo sech(r/r sech(r/roo) = I) = Ioo/cosh(r/r/cosh(r/roo) = 2I) = 2Ioo/(e/(er/ror/ro+e+e--

r/ror/ro))

(Vaduvescu et al., AJ 130, 2005)(Vaduvescu et al., AJ 130, 2005)

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Surface photometry of BCDs: Surface photometry of BCDs:

Sech for the old extended component: Sech for the old extended component: IISS = I = I0S0S sech(r/rsech(r/r0S0S) )

plus Gaussian for the young starburst: plus Gaussian for the young starburst: IIGG=I=I0G0G exp[- exp[-1/2 (r/r1/2 (r/r0G0G))22]]

(Vaduvescu, Richer & McCall, AJ 131, 2006)(Vaduvescu, Richer & McCall, AJ 131, 2006) I = II = ISS + I+ IGG

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Surface Photometry – tool for dI and BCD Surface Photometry – tool for dI and BCD distinction: distinction:

NGC 1569 – NGC 1569 –

dI or BCD?dI or BCD?

Sech plus Sech plus Gaussian Gaussian fitting (BCD?)fitting (BCD?)

Sech fitting Sech fitting (dI?)(dI?)

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Stellar Photometry – CMDs of dIs: Stellar Photometry – CMDs of dIs:

Selected star Selected star cataloguecatalogue

(stars from galaxy)(stars from galaxy)

Stars in the field Stars in the field

(from Milky Way)(from Milky Way)

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Stellar Photometry – CMDs of dIs: Stellar Photometry – CMDs of dIs:

Two details in most CMDs: Two details in most CMDs: Blue finger (J – KBlue finger (J – Kss 1 mag) – O-rich RGB stars 1 mag) – O-rich RGB stars

Red tail (1 Red tail (1 J – K J – Kss 2.5 mag) – TP-AGB stars 2.5 mag) – TP-AGB stars

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Surface PhotometrySurface Photometry

dIs – three magnitudes: dIs – three magnitudes:

Isophotal MIsophotal MII – unresolved, measured from ellipses; – unresolved, measured from ellipses;

Sech MSech MSS – modeled from sech law applied to the – modeled from sech law applied to the unresolved component (no giant stars, thus mostly old unresolved component (no giant stars, thus mostly old populations); populations);

Total MTotal MTT – add the resolved stars from selected star – add the resolved stars from selected star catalog. catalog.

BCDs – four magnitudes: BCDs – four magnitudes:

Isophotal MIsophotal MII – measured from ellipses; – measured from ellipses;

Sech MSech MSS – model of the outer component (old – model of the outer component (old populations); populations);

Gaussian MGaussian MGG – model of the inner starburst (young – model of the inner starburst (young stars); stars);

Total MTotal MTT – include M – include MSS and M and MGG

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Fraction of light from a Fraction of light from a starburststarburst

Fraction of light of a burst of Fraction of light of a burst of

star formation contributed bystar formation contributed by

stars brighter than Mstars brighter than MKK= –7.5= –7.5

mag with respect to the total mag with respect to the total

flux from all stars, as a flux from all stars, as a functionfunction

of stellar age. of stellar age.

For bursts younger than 3 For bursts younger than 3 Gyr,Gyr,

most of the light comes frommost of the light comes from

stars brighter than Mstars brighter than MKK= –7.5 = –7.5 Based on population Based on population synthesissynthesis

(Girardi et al, 2000, 2002)(Girardi et al, 2000, 2002)

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Structural properties of dIsStructural properties of dIs

Scale length correlates withScale length correlates with

absolute magnitude.absolute magnitude.

rr00=(-0.81=(-0.810.24)+(-0.24)+(-0.070.070.01)M0.01)MSS

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Structural properties of dIs Structural properties of dIs (continued)(continued)

Semimajor axis correlates Semimajor axis correlates withwith

absolute magnitude. absolute magnitude.

rr2222=(-5.34=(-5.340.40)+(-0.40)+(-0.380.380.02)M0.02)MSS

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Structural properties of dIs Structural properties of dIs (continued)(continued)

Central surface brightness Central surface brightness

shows a trend with absoluteshows a trend with absolute

magnitude. magnitude.

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Structural properties of dIs Structural properties of dIs (continued)(continued)

Total colour has a trend withTotal colour has a trend with

the absolute magnitude. the absolute magnitude.

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Structural properties of dIs Structural properties of dIs (continued)(continued)

The Tully-Fisher relation for The Tully-Fisher relation for dIsdIs

solid fit – our data; dashed – solid fit – our data; dashed – P&TP&T

The “dI Fundamental Plane”The “dI Fundamental Plane”

(Vaduvescu et al., AJ 130, (Vaduvescu et al., AJ 130, 2005)2005)

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Structural properties of Structural properties of BCDsBCDs

Scale length has a trend Scale length has a trend withwith

the absolute magnitude. the absolute magnitude.

(dashed line shows the dI (dashed line shows the dI fit)fit)

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Structural properties of BCDs (continued)Structural properties of BCDs (continued)

Central surface brightness Central surface brightness has has

a trend with the absolutea trend with the absolute

magnitude. magnitude.

(dashed line shows the dI (dashed line shows the dI fit)fit)

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BCDs on the dI Fundamental PlaneBCDs on the dI Fundamental Plane

BCDs appear to lie on the dI FPBCDs appear to lie on the dI FP

(Vaduvescu, Richer & McCall, (Vaduvescu, Richer & McCall,

AJ 131, 2006)AJ 131, 2006)

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Structural Properties of dEsStructural Properties of dEs

Fit SBPs of dEs using the exp: Fit SBPs of dEs using the exp:

I = II = I00 exp(-r/r exp(-r/r00))

Scale length correlates with Scale length correlates with

absolute magnitudeabsolute magnitude

(dashed line shows the dI fit)(dashed line shows the dI fit)

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Structural Properties of dEs (continued)Structural Properties of dEs (continued)

Semimajor axis correlates Semimajor axis correlates with with

absolute magnitudeabsolute magnitude

(dashed line shows the dI fit)(dashed line shows the dI fit)

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Structural Properties of dEs (continued)Structural Properties of dEs (continued)

Central surface brightnessCentral surface brightness

correlates with absolutecorrelates with absolute

magnitudemagnitude

(dashed line shows the dI fit)(dashed line shows the dI fit)

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Structural properties of dEs Structural properties of dEs (continued)(continued)

Tully-Fisher relation for dEsTully-Fisher relation for dEs

is scattered is scattered dEs lie on the dI FP dEs lie on the dI FP

(Vaduvescu & McCall, (Vaduvescu & McCall,

IAU Colloquium 198, 2005)IAU Colloquium 198, 2005)

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Spectroscopy of HII regions of BCDsSpectroscopy of HII regions of BCDs

Determine the oxygen abundance, 12+log(O/H), using: Determine the oxygen abundance, 12+log(O/H), using:

Direct [OIII] Direct [OIII] 4363 (Osterbrock, 1989)4363 (Osterbrock, 1989)

given a temperature and density; given a temperature and density; The bright-line method RThe bright-line method R2323 (Pagel et al., 1979) (Pagel et al., 1979)

RR2323=( I([OII] =( I([OII] 3727) + I([OIII] 3727) + I([OIII] 4959,5007) ) / I(H4959,5007) ) / I(H))

Data reduction performed with:Data reduction performed with:

INTENS to fit lines INTENS to fit lines

(McCall & Mundy, 1980); (McCall & Mundy, 1980); SNAP to measure linesSNAP to measure lines

(Krawchuck, et al, 1997) (Krawchuck, et al, 1997)

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Spectroscopy of HII regions of BCDs Spectroscopy of HII regions of BCDs (continued)(continued)

Reduced combined Reduced combined

spectrum of VCC 459spectrum of VCC 459

(Gemini-N GMOS (Gemini-N GMOS data)data)

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Chemical properties of dwarf galaxiesChemical properties of dwarf galaxies

Luminosity-metallicityLuminosity-metallicity

relation for dIsrelation for dIs

12 + log(O/H) =12 + log(O/H) =

(-0.13 (-0.13 0.01) M 0.01) MKK++

(5.77 (5.77 0.21) 0.21)

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Chemical properties of dwarf galaxies Chemical properties of dwarf galaxies (continued)(continued)

Luminosity-metallicityLuminosity-metallicity

relation for BCDsrelation for BCDs

12 + log(O/H) =12 + log(O/H) =

(-0.24 (-0.24 0.03) M 0.03) MKK++

(3.88 (3.88 0.53) 0.53)

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Chemical properties of dwarf galaxies Chemical properties of dwarf galaxies (continued)(continued)

Gas mass-metallicityGas mass-metallicity

relation for dIs & BCDsrelation for dIs & BCDs

dI fit (solid line): dI fit (solid line):

12 + log(O/H) =12 + log(O/H) =

(5.26 (5.26 0.46) + 0.46) +

(0.32 (0.32 0.06) log(M 0.06) log(Mgasgas))

Lee, 2001 (dotted line)Lee, 2001 (dotted line)

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Chemical properties of dwarf galaxies Chemical properties of dwarf galaxies (continued)(continued)

Mass-metallicityMass-metallicity

relation for dIs & BCDsrelation for dIs & BCDs

dI fit (solid line): dI fit (solid line):

12 + log(O/H) =12 + log(O/H) =

(5.04 (5.04 0.44) + 0.44) +

(0.34 (0.34 0.05) log(M 0.05) log(Mbarybary))

Lee, 2001 (dotted line)Lee, 2001 (dotted line)

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Chemical properties of dwarf galaxies Chemical properties of dwarf galaxies (continued)(continued)

Gas fraction-metallicityGas fraction-metallicity

relation for dIs & BCDsrelation for dIs & BCDs

= M= Mgasgas/(M/(Mgasgas+M+Mstarsstars))

Closed-box modelClosed-box model

Lee, 2001 (dotted line)Lee, 2001 (dotted line)

dIs and BCDsdIs and BCDs

appear to fit the appear to fit the

closed box modelclosed box model

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Conclusions: Conclusions:

In dIs from the LV (D<5 Mpc) observed at CFHT we In dIs from the LV (D<5 Mpc) observed at CFHT we resolvedresolved

stars as faint as Mstars as faint as MKK= – 7.5 mag (giants younger than ~8.5 = – 7.5 mag (giants younger than ~8.5 Gyr);Gyr);

Resolved/Total flux ratios in dIs in K are less than 5% (10% Resolved/Total flux ratios in dIs in K are less than 5% (10% in J);in J);

Correlated with population synthesis, the unresolved Correlated with population synthesis, the unresolved componentcomponent

can be regarded as old;can be regarded as old;

Surface brightness profiles of dIs can be fitted with sech Surface brightness profiles of dIs can be fitted with sech function; function;

Surface brightness profiles of BCDs can be fitted with sech Surface brightness profiles of BCDs can be fitted with sech (to(to

model the underlying extended old component) plus model the underlying extended old component) plus Gaussian (toGaussian (to

model the inner young starburst);model the inner young starburst);

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Conclusions Conclusions (continued): (continued):

Sizes of dIs and BCDs correlates with brightness;Sizes of dIs and BCDs correlates with brightness; Central brightness of dIs and BCDs correlates with Central brightness of dIs and BCDs correlates with

brightness;brightness; Colours of dIs correlate with brightness;Colours of dIs correlate with brightness;

CMDs of resolved stars in dIs show two details: a blue CMDs of resolved stars in dIs show two details: a blue finger finger

(O-rich intermediate-age and old AGB bright stars), and (O-rich intermediate-age and old AGB bright stars), and a red tail (TP-AGB stars);a red tail (TP-AGB stars);

BCDs and dIs are similar, structurally and dynamically; BCDs and dIs are similar, structurally and dynamically;

dEs follow the structural correlations of dIs, matching dEs follow the structural correlations of dIs, matching closelyclosely

the dI Fundamental Plane, suggesting an intimate link the dI Fundamental Plane, suggesting an intimate link betweenbetween

the two systems; the two systems;

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Conclusions Conclusions (continued): (continued):

dIs, BCDs & dEson the dI

Fundamental Plane

4141

Conclusions Conclusions (continued): (continued):

Metallicity (oxygen abundances) of dIs and BCDs Metallicity (oxygen abundances) of dIs and BCDs correlates with stellar mass, gas mass, baryonic mass, correlates with stellar mass, gas mass, baryonic mass, and the gas fractionand the gas fraction

(dIs only). More massive systems contain more metals; (dIs only). More massive systems contain more metals;

BCDs align with dIs on the metallicity – baryonic mass BCDs align with dIs on the metallicity – baryonic mass relation,relation,

suggesting similar evolutionary connections between the suggesting similar evolutionary connections between the two; two;

Overall, BCDs appear to be dIs observed in a bursting Overall, BCDs appear to be dIs observed in a bursting phase; phase;

Based on the metallicity – gas fraction relation, it seems Based on the metallicity – gas fraction relation, it seems that dIs and BCDs obey the closed box model; that dIs and BCDs obey the closed box model;

dEs appear to represent the final outcome of dIs (or dEs appear to represent the final outcome of dIs (or BCDs), BCDs),

after all the gas is removed from the system. after all the gas is removed from the system.

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Future Projects: Future Projects:

Publish Chapters 7 & 8 (chemical properties of dwarfs) -Publish Chapters 7 & 8 (chemical properties of dwarfs) -Vaduvescu, McCall and Richer, AJ 2006bVaduvescu, McCall and Richer, AJ 2006b to be sent soon; to be sent soon;

Enhance the sample later (spectroscopy needed); Enhance the sample later (spectroscopy needed);

Study the dI Fundamental Plane at the bright end based Study the dI Fundamental Plane at the bright end based onon

2MASS (2MASS (Vaduvescu, 2006cVaduvescu, 2006c in work); in work);

Add new dIs data at the faint end – two runs at Add new dIs data at the faint end – two runs at SAAO/IRSF, CFHT/WIRCAM, two new runs at ESO/NTT and SAAO/IRSF, CFHT/WIRCAM, two new runs at ESO/NTT and CTIO/Blanco – Fingerhut, McCall, Vaduvescu, Rekola, et CTIO/Blanco – Fingerhut, McCall, Vaduvescu, Rekola, et al (in work); al (in work);

Study L-Z and mass-Z relation for dwarfs in clusters – Study L-Z and mass-Z relation for dwarfs in clusters – Vaduvescu, Vilchez, Iglesias-Paramo, Kehrig, et al (in Vaduvescu, Vilchez, Iglesias-Paramo, Kehrig, et al (in work); work);

Get a job Get a job

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Thank you !Thank you !

Also we’d like to thank ESO for granting us time to Also we’d like to thank ESO for granting us time to observe observe

on the NTT. For me, observing at La Silla was a dream on the NTT. For me, observing at La Silla was a dream which came true! which came true!

In case you’ve wondered: In case you’ve wondered:

Background image: NGC 1569 at CFHT 2002Background image: NGC 1569 at CFHT 2002

4444

In preparation for an observing night In preparation for an observing night

(La Silla, 2 July 2006, courtesy of my Nikon D50)(La Silla, 2 July 2006, courtesy of my Nikon D50)