Journal Article

Testing spectral models for stellar populations with star clusters – I. Methodology

Roberto Cid Fernandes and Rosa M. González Delgado

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 403, issue 2, pages 780-796
Published in print April 2010 | ISSN: 0035-8711
Published online March 2010 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2009.16153.x
Testing spectral models for stellar populations with star clusters – I. Methodology

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High-resolution spectral models for simple stellar populations (SSP) developed in the past few years have become a standard ingredient in studies of stellar population of galaxies. As more such models become available, it becomes increasingly important to test them. In this and a companion paper, we test a suite of publicly available evolutionary synthesis models using integrated optical spectra in the blue-near-UV range of 27 well-studied star clusters from the work of Leonardi and Rose spanning a wide range of ages and metallicities. Most (23) of the clusters are from the Magellanic Clouds. This paper concentrates on the methodological aspects of spectral fitting. The data are fitted with SSP spectral models from Vazdekis and collaborators, based on the Medium-resolution INT Library of Empirical Spectra. Best-fitting and Bayesian estimates of age, metallicity and extinction are presented, and degeneracies between these parameters are mapped. We find that these models can match the observed spectra very well in most cases, with small formal uncertainties in t, Z and AV. In some cases, the spectral fits indicate that the models lack a blue old population, probably associated with the horizontal branch. This methodology, which is mostly based on the publicly available code starlight, is extended to other sets of models in Paper II, where a comparison with properties derived from spatially resolved data (colour–magnitude diagrams) is presented. The global aim of these two papers is to provide guidance to users of evolutionary synthesis models and empirical feedback to model makers.

Keywords: techniques: spectroscopic; galaxies: evolution; Magellanic Clouds; galaxies: star clusters; galaxies: stellar content

Journal Article.  11650 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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