Claudia Maraston Oxford 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 + empirical recipes Isochrone Synthesis Bruzual & Charlot93;03 Worthey94 Vazdekis+96 Pegase97 Starburst99 Jimenez+04 Fuel Consumption Buzzoni89 - only old ages Maraston98;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 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

Claudia Maraston Venice 2006 From Ferraro et al. 2004, ApJ Girardi et al. 00 Padova tracks Frascati tracks RGB phase-transition: Frascati tracks are well-calibrated Calibration with GCs 1.Overshooting and RGB onset

Claudia Maraston Venice 2006 Calibration with LMC globular clusters Maraston 2005, MNRAS, 362, AGB

Claudia Maraston Venice 2006 Calibration of synthetic optical colours - cf. van der Wel’s talk - other colour- colour diagrams in Maraston05 MC GCs 3<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 Masses get 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