Critical Steps in

Population Synthesis

Alessandro Bressan

MAGPOP Summer School - Budapest, Hungary, 2006. August 23-25

What is Pop. Synth.An ensemble of tools used to predict properties of stellar systems

• resolved systems

C-M diagrams

• unresolved systems

Magnitudes (colours)

Spectra

Narrow band indices

Resolved system: Old Population

Resolved system: Young

Population

Resolved system:

“Complex” Population

Wide field imaging and Star Formation History in the Local Group Galaxies (Sagittarius)

Held et al 04

UnresolvedSystems

Bertone et al 05

The Isochrone

EVOLUTIONARYTRACKS

THEORETICAL ISOCHRONE

ISOCHRONEin the

OBSERVED SYSTEM

BOLOMETRICCORRECTIONS

MULTI BANDOBSERVATIONS OF

STARS

STELLARMODELS

• Y2 (Yonsei-Yale) Isochrones (Demarque, Yi et al. 83-06..)http://www.astro.yale.edu/demarque/yyiso.html

• Padova database of stellar evolutionary tracks and isochrones http://pleiadi.pd.astro.it/

Bertelli, Bressan, Chiosi, Girardi et al (84-06)

• GENEVA GRIDS OF STELLAR EVOLUTION MODELSMaeder, Meynet, Schaerer et al (84-06..)

http://obswww.unige.ch/~mowlavi/evol/stev_database.html

• Achim Weiss (http://www.mpa-garching.mpg.de/stars/index.shtml)

• Santi Cassisi (http://www.te.astro.it/osservatorio/personale/cassisi/)

• Oscar Straniero (http://www.te.astro.it/osservatorio/personale/straniero/oscar.html)

Phot. Systems

The Temperature scale

The Bolometric Corrections

Bertone et al 05

Isochrones

The C-M DiagramIsochrone IMF

C-M Diagram

Observationalm Effects:

• Completeness• Errors• Real Binaries• LOS Binaries

SSP

Case Study for the

Evolution of

Low Mass Stars:

Globular Cluster

NGC5024

Piotto et al 2002

Ev. Tracks with suited composition

No TP-AGB in Tracks!

Ev. Tracks vs. Isochrones

No Binaries- No Errors

10% Binaries

Errors & no Binaries

Errors and 5% Binaries

Errors & 20% Binaries

LF

IMF

Stellar Lifetimes

N(MV)

The Integrated Spectrum

EVOLUTIONARYTRACKS

STELLAR ATMOSPHERES

Theoretical Isochrone

Isochrone

Atmosph. Models vs Observ.

High Res Integrated Spectrum

Ca4227

G4300