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Claudia Maraston Oxford University

The AGB phase and the ages and masses of high-z galaxies. Claudia Maraston Oxford University. Galaxy Evolution through Cosmic Times- Venezia, 2006. Constraining Galaxy Formation/Evolution. Stars : stellar evolution independent of cosmological models.

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Claudia Maraston Oxford University

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  1. The AGB phase and the ages and masses of high-z galaxies Claudia Maraston Oxford University Galaxy Evolution through Cosmic Times- Venezia, 2006

  2. Constraining Galaxy Formation/Evolution Stars: stellar evolution independent of cosmological models 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 Claudia MarastonVenice 2006

  3. 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 MarastonVenice 2006

  4. Energetics of Stellar Populations:Three Regimes Main Sequence + He-burning stars dominate the light of young stellar populations AGB stars dominate the light of intermediate-age stellar populations RGB stars dominate the light of old stellar populations Claudia MarastonVenice 2006

  5. 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 MarastonVenice 2006

  6. 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 MarastonVenice 2006

  7. Results: Model SEDs www.astro-physics.ox.ac.uk/~maraston Maraston 2005, MNRAS, 362, 799 Claudia MarastonVenice 2006

  8. Calibration with GCs1.Overshooting and RGB onset RGB phase-transition: Frascati tracks are well-calibrated Frascati tracks Girardi et al. 00 Padova tracks From Ferraro et al. 2004, ApJ Claudia MarastonVenice 2006

  9. 2. AGB Calibration with LMC globularclusters Maraston 2005, MNRAS, 362, 799 Claudia MarastonVenice 2006

  10. Calibration of synthetic optical colours - cf. van der Wel’s talk - MC GCs 3<SWB<6 other colour- colour diagrams in Maraston05 Claudia MarastonVenice 2006

  11. Ages & Masses of high-z galaxies Depend on the adopted evolutionary population synthesis Claudia MarastonVenice 2006

  12. Effect of spectral synthesis models on high-z galaxies. 1. HUDF Claudia MarastonVenice 2006 Maraston, Daddi + 06, ApJ

  13. HUDF galaxies.2. Claudia MarastonVenice 2006

  14. Undetected in MIPS! OLDER THAN UNIVERSE HUDF galaxies.3. Maraston, Daddi + 06 Claudia MarastonVenice 2006

  15. Stellar Masses of HUDF Galaxies Masses get lower Maraston et al.06 Claudia MarastonVenice 2006

  16. Photo-z Claudia MarastonVenice 2006

  17. data from Rigoupolou et al.05 Near-IR selected z ~ 3 galaxies (sp. redshifts) Claudia MarastonVenice 2006 Maraston et al. in prep

  18. 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 massesformation models • Lower reddening • Effect on photometric redshifts (details in Maraston et al. 06) Claudia MarastonVenice 2006

  19. Formation redshifts in prep. with Laura Perry, D. Thomas - Oxford Claudia MarastonVenice 2006

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