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Stellar Evolution and Stellar Populations in Galaxies

Published online by Cambridge University Press:  07 August 2017

André Maeder*
Affiliation:
Geneva Observatory CH-1290 Sauverny, Switzerland

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Models of population synthesis are resting on an ensemble of other models, data and assumptions, in particular the models of stellar evolution, the data on initial compositions, the data on stellar spectra, the initial mass function (IMF), the star formation rate (SFR), the infall rate, etc… Here we shall concentrate on the properties of stellar models and their consequences for the global properties of stellar populations in galaxies.

The basic link between star properties and population synthesis is expressed in the so-called fuel consumption theorem (cf. Renzini and Buzzoni, 1986). It says that the contribution of stars in any post main sequence stage to the total luminosity of a star population is proportional to the amount of fuel burnt in the considered evolutionary stage. The demonstration of this theorem is rather straightforward. And although it is not used in recent population synthesis (cf. Guideroni and Rocca–Volmerange, 1987; Charlot and Bruzual, 1990), its didactical value is great. It shows how the integrated properties of star populations in galaxies directly depend on stellar internal properties. Indeed, the amount of fuel burnt in a given stage depends, in turn, on many physical assumptions in the models, such as the nuclear reaction rates, the opacities, convection and overshooting, mass loss, mixing processes, etc… Thanks to the above theorem, the effect of different model assumptions on population synthesis can be predicted, at least qualitatively.

Information

Type
I. The Stellar Populations in the Milky Way
Copyright
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