Measuring Ages and Elemental Abundances from Unresolved Stellar Populations: Fe, Mg, C, N, and Ca - AstrophysicsReport as inadecuate

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Abstract: We present a method for determining mean light-weighted ages and abundancesof Fe, Mg, C, N, and Ca, from medium resolution spectroscopy of unresolvedstellar populations. The method, pioneered by Schiavon 2007, is implementedin a publicly available code called EZ Ages. The method and error estimationare described, and the results tested for accuracy and consistency, byapplication to integrated spectra of well-known Galactic globular and openclusters. Ages and abundances from integrated light analysis agree with studiesof resolved stars to within +-0.1 dex for most clusters, and to within +-0.2dex for nearly all cases. The results are robust to the choice of Lick indicesused in the fitting to within +-0.1 dex, except for a few systematicdeviations which are clearly categorized. The realism of our error estimates ischecked through comparison with detailed Monte Carlo simulations. Finally, weapply EZ Ages to the sample of galaxies presented in Thomas et al. 2005 andcompare our derived values of age, Fe-H, and alpha-Fe to their analysis. Wefind that alpha-Fe is very consistent between the two analyses, that ages areconsistent for old Age > 10 Gyr populations, but show modest systematicdifferences at younger ages, and that Fe-H is fairly consistent, with smallsystematic differences related to the age systematics. Overall, EZ Agesprovides accurate estimates of fundamental parameters from medium resolutionspectra of unresolved stellar populations in the old and intermediate-ageregime, for the first time allowing quantitative estimates of the abundances ofC, N, and Ca in these unresolved systems. The EZ Ages code can be downloaded atthis http URL

Author: Genevieve J. Graves, Ricardo P. Schiavon


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