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

2008/03/10 by Genevieve J. Graves, Ricardo P. Schiavon · 142 citations
Physics and Astronomy · #Astronomical spectroscopy #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Galaxy #Globular cluster #Monte Carlo method #Spectral line #Stars #Stellar population #Stellar, planetary, and galactic studies #Systematic error #astro-ph

paper · pdf · doi:10.1086/588097

published in The Astrophysical Journal Supplement Series 177(2), 446-464 (Institute of Physics) · Accepted to ApJS

arxiv created 2008/03/10 · openalex publication_date 2008/07/31 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05

Abstract

We present a method for determining mean light-weighted ages and abundances of Fe, Mg, C, N, and Ca from medium-resolution spectroscopy of unresolved stellar populations. The method is implemented in a publicly available code called EZ_Ages. The method and error estimation are described, and the results tested for accuracy and consistency, by application to integrated spectra of well-known Galactic globular and open clusters. Ages and abundances from integrated light analysis agree with studies of resolved stars to within ±0.1 dex for most clusters, and to within ±0.2 dex for nearly all cases. The results are robust to the choice of Lick indices used in the fitting to within ±0.1 dex, except for a few systematic deviations that are clearly categorized. The realism of our error estimates is checked through comparison with detailed Monte Carlo simulations. Finally, we apply EZ_Ages to the sample of galaxies presented in Thomas et al. (2005) and compare our derived values of age, [Fe/H], and [α/Fe] to their analysis. We find that [α/Fe] is very consistent between the two analyses, that ages are consistent for old (age > 10 Gyr) populations but show modest systematic differences at younger ages, and that [Fe/H] is fairly consistent, with small systematic differences related to the age systematics. Overall, EZ_Ages provides accurate estimates of fundamental parameters from medium-resolution spectra of unresolved stellar populations in the old and intermediate-age regime, for the first time allowing quantitative estimates of the abundances of C, N, and Ca in these unresolved systems.

Citations

• Population Synthesis in the Blue. IV. Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations
• The Spectroscopic Age of 47 Tucanae
• Oxygen trends in the Galactic thin and thick disks
• An Abundance Analysis for Four Red Horizontal-Branch Stars in the Extremely Metal-Rich Globular Cluster NGC 6528
• Evolutionary tracks and isochrones for low- and intermediate-mass stars: From 0.15 to 7 M_\odot, and from Z=0.0004 to 0.03
• Integrated spectroscopy of bulge globular clusters and fields

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• EARLY-TYPE GALAXY ARCHEOLOGY: AGES, ABUNDANCE RATIOS, AND EFFECTIVE TEMPERATURES FROM FULL-SPECTRUM FITTING
• Massive Quenched Galaxies at z ∼ 0.7 Retain Large Molecular Gas Reservoirs

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