Claudia Maraston Institute of Cosmology and Gravitation University of Portsmouth - UK

Claudia Maraston

Institute of Cosmology and GravitationUniversity of Portsmouth - UK

Stellar Population ModelsInterpreting observations

Colouring simulations

Galaxies in real life and in the simulations Leiden - 19 September 2008

Claudia Maraston Leiden 19 September 2008

Outline Stellar Population Models: basic ingredients

• Effect of model prescriptions on: interpreting the data ages, masses, SFR, IMF, … predicting synthetic galaxies

Effect of the considered wavelength range

Solved a mismatch between the models and the SLOAN colours of luminous red galaxies is solved


Stellar Population Model

Adding up the energetics of stellar phases

- MS- SGB- Red Giant Branch- HB- (E-AGB)- TP-AGB TP-AGB + RGB decide when the model SED turns red

Maraston 2005


Magellanic Clouds globularclusters to test

the models

Maraston 2005

TP-AGB

Claudia Maraston Leiden 19 September 2008Ferraro et al. 2004

Padova tracks

M05

Data exclude late RGB onset

Onset of the Red Giant Branch


Effect of stellar evolution on properties derived from data

• TP-AGB: lower ages/ lower stellar masses/lower dust content

Maraston et al. 06, van der Wel 05.06; Wyuts et al. 07; Rodighiero et al. 07; Cimatti et al. 08; Franx et al. 08; cf. Ivo Labbe’s talk

• non overshooting RGB onset: same effect Maraston et al. 2006


Age/metallicity degeneracy

The same 4000 AA break!!! The near-IR is fundamentalto break the degeneracies


Near-IR helps always even for starforming galaxies

z~2 GOODSBzK starforminggalaxies

in prep. withJ. PforrE. DaddiA. RenziniA. Cimatti


Effect of stellar pop model on semi-analytic galaxiesGALICS

semi-analitycmodel +

BC/Pegase

M05

Tonini,CM,DevriendtThomas,Silk,in prep.


Fixing the gri colors of luminous red galaxies

Wake, Nichol et al. 06

A persistent problem in matchingthe g,r,i colours of LuminousRed Galaxies in SLOAN over a broad z range

Eisenstein et al. 2001 arbitrary offsetthe model up to 0.1 mag


Very low level of sf excluded


Summary• Ingredients of stellar population models - TP-AGB, RGB - determine the empirical relations - ages, stellar masses, SFR - derived from data• Wavelength range: including the near-IR is crucial • SP models determine the spectra of synthetic galaxies from semi-analytic models or simulations• Model galaxies get redder at younger ages because of the TP-AGB/RGB … Tully-Fisher relation … Colour-magnitude relation …. Luminosity functon• Long-standing mismatches between models and observed SLOAN

colours in the rest-frame optical have been solved • To model the colour evolution of Luminous Red Galaxies in SLOAN up

to z ~ 0.8 requires: empirical spectra in the model and the presence of 3% by mass of metal-poor stars

--- chemical evolution or accretion ?

Claudia Maraston Institute of Cosmology and Gravitation University of Portsmouth - UK

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