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Claudia Maraston Oxford University The AGB phase and the ages and masses of high-z galaxies Galaxy...
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Transcript of Claudia Maraston Oxford University The AGB phase and the ages and masses of high-z galaxies Galaxy...
Claudia MarastonOxford University
The AGB phase and
the ages and masses of high-z galaxies
Galaxy Evolution through Cosmic Times- Venezia, 2006
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
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
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
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
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)
Claudia Maraston Venice 2006
Results: Model SEDs
Maraston 2005, MNRAS, 362, 799 www.astro-physics.ox.ac.uk/~maraston
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
Claudia Maraston Venice 2006
Calibration with LMC globularclusters
Maraston 2005, MNRAS, 362, 799
2. AGB
Claudia Maraston Venice 2006
Calibration of synthetic optical colours - cf. van der Wel’s talk -
othercolour-colourdiagramsin Maraston05
MC GCs3<SWB<6
Claudia Maraston Venice 2006
Ages & Masses of high-z galaxies
Depend on the adopted evolutionary population synthesis
Claudia Maraston Venice 2006
Effect of spectral synthesis models on high-z galaxies. 1. HUDF
Maraston, Daddi + 06, ApJ
Claudia Maraston Venice 2006
HUDF galaxies.2.
Claudia Maraston Venice 2006
OLDER THAN UNIVERSE
Maraston, Daddi + 06
HUDF galaxies.3.
Undetected in MIPS!
Claudia Maraston Venice 2006
Stellar Masses of HUDF Galaxies
Maraston et al.06
Massesget lower
Claudia Maraston Venice 2006
Photo-z
Claudia Maraston Venice 2006
Near-IR selected z ~ 3 galaxies (sp. redshifts)
Maraston et al. in prep
data from Rigoupolou et al.05
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)
Claudia Maraston Venice 2006
Formation redshifts
in prep. with Laura Perry, D. Thomas - Oxford