claudia maraston oxford university the agb phase and the ages and masses of high-z galaxies galaxy...
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![Page 1: Claudia Maraston Oxford University The AGB phase and the ages and masses of high-z galaxies Galaxy Evolution through Cosmic Times- Venezia, 2006](https://reader030.vdocuments.net/reader030/viewer/2022032800/56649d485503460f94a23ffa/html5/thumbnails/1.jpg)
Claudia MarastonOxford University
The AGB phase and
the ages and masses of high-z galaxies
Galaxy Evolution through Cosmic Times- Venezia, 2006
![Page 2: Claudia Maraston Oxford University The AGB phase and the ages and masses of high-z galaxies Galaxy Evolution through Cosmic Times- Venezia, 2006](https://reader030.vdocuments.net/reader030/viewer/2022032800/56649d485503460f94a23ffa/html5/thumbnails/2.jpg)
Claudia Maraston Venice 2006
Constraining Galaxy Formation/Evolution
Needs a stellar population model
Results rely fully on the adopted evolutionary population synthesis code
Ages, star formation histories, stellar masses M*, photo-z, etc. of galaxies from integrated light
Stars: stellar evolution independent of cosmological models
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Claudia Maraston Venice 2006
Evolutionary Population Synthesis
Stellar Population model adding up the energetics of all stellar phases following stellar evolution i.e. stellar tracks and isochrones + empiricalrecipes
Isochrone SynthesisBruzual & Charlot93;03Worthey94Vazdekis+96Pegase97Starburst99 Jimenez+04
Fuel ConsumptionBuzzoni89 - only old agesMaraston98;05
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Claudia Maraston Venice 2006
Energetics of Stellar Populations:Three Regimes
AGB stars dominate the light of intermediate-age stellar populations
Main Sequence +
He-burning stars dominate the light of young stellar populations
RGB stars dominate the light of old stellar populations
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Claudia Maraston Venice 2006
The (Curable) Uncertainties
• Treatment of AGB (mass-loss): tracks uncertain imp at 0.2 < t/Gyr < 2, wav. > 5000 AA• Onset of RGB and MS lifetime (overshooting): • imp at 0.2 < t/Gyr < 3, all lambdas• All critical at high-z, in particular (but not
only) when near-IR sampled
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Claudia Maraston Venice 2006
Two Classes of Population Synthesis Models
• Stellar tracks w overshooting- Padova
+ theoretical TP-AGB (BC03,Pegase, Starburst99, etc.)
• Stellar tracks w/o overshooting -Frascati- + TP-AGB semi-empirical (Maraston)
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Claudia Maraston Venice 2006
Results: Model SEDs
Maraston 2005, MNRAS, 362, 799 www.astro-physics.ox.ac.uk/~maraston
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Claudia Maraston Venice 2006From Ferraro et al. 2004, ApJ
Girardi et al. 00 Padova tracks
Frascati tracks
RGB phase-transition: Frascati tracks are well-calibrated
Calibration with GCs1.Overshooting and RGB onset
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Claudia Maraston Venice 2006
Calibration with LMC globularclusters
Maraston 2005, MNRAS, 362, 799
2. AGB
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Claudia Maraston Venice 2006
Calibration of synthetic optical colours - cf. van der Wel’s talk -
othercolour-colourdiagramsin Maraston05
MC GCs3<SWB<6
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Claudia Maraston Venice 2006
Ages & Masses of high-z galaxies
Depend on the adopted evolutionary population synthesis
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Claudia Maraston Venice 2006
Effect of spectral synthesis models on high-z galaxies. 1. HUDF
Maraston, Daddi + 06, ApJ
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Claudia Maraston Venice 2006
HUDF galaxies.2.
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Claudia Maraston Venice 2006
OLDER THAN UNIVERSE
Maraston, Daddi + 06
HUDF galaxies.3.
Undetected in MIPS!
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Claudia Maraston Venice 2006
Stellar Masses of HUDF Galaxies
Maraston et al.06
Massesget lower
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Claudia Maraston Venice 2006
Photo-z
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Claudia Maraston Venice 2006
Near-IR selected z ~ 3 galaxies (sp. redshifts)
Maraston et al. in prep
data from Rigoupolou et al.05
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Claudia Maraston Venice 2006
Summary
• Galaxy properties depend on spectral synthesis models
• Recipes for red giants - AGB and RGB - are crucial• Effects of models with empirical AGB
(Maraston98;05) include:• Ages are lower, always smaller than the age of
the Universe • Lower formation redshifts Impact on galaxy• Lower stellar masses formation models• Lower reddening• Effect on photometric redshifts (details in Maraston et al. 06)
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Claudia Maraston Venice 2006
Formation redshifts
in prep. with Laura Perry, D. Thomas - Oxford