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Metallicity of Unresolved Stellar Populations

Published online by Cambridge University Press:  07 August 2017

M.G. Edmunds*
Affiliation:
Department of Physics and Astronomy, University of Wales College of Cardiff, P.O.Box 913, CARDIFF CF1 3TH, U.K.

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The determination of the metallicity of an unresolved population is not easy. An obvious problem is that stars of the same mass, but different metallicities, evolve at different rates and have different luminosities. For example, metal poor red giants are considerably brighter in the optical region than corresponding metal rich stars. The “mean” abundance for a stellar population therfore depends on whether the mean is taken with respect to mass, star number or luminosity. It is inevitable that observational work weights by luminosity, while chemical evolution models usually weight by mass. The two weightings can give rather different means, which may also depend on the “metallicity structure” - i.e. the relative numbers of stars of different metallicities, and rough calculations show that metallicity indicators like colours could give 0.3 dex lower abundance than the mass-weighted mean, if uniform (i.e. single metallicity population) calibrators have been used.

Type
III. The Stellar Populations of Non-Resolved Galaxies
Copyright
Copyright © Kluwer 

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