abundance globular cluster

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a r X i v : a s t r o p h / 0 3 0 7 0 6 9 v 2  3  J u l  2 0 0 3 Carnegie Observatories Astrophysics Series, Vol. 4: Origin and Evolution of the Elements ed. A. McWilliam and M. Rauch (Cambridge: Cambridge Univ. Press) Abundances from the Integrated Light of Globular Clusters and Galaxies S. C. TRAGER Kaptey n Astrono mical Institute, Groni ngen, The Netherla nds Abstract It is currently impossible to determine the abundances and ages of the stellar populations of distant, dense stellar systems star by star. Therefore, methods to analyze the composite light of stellar systems are required. I review the modelling and analysis of integrated spectra of the stellar populations of individual globular clusters, globular cluster systems, early-type galaxies, and the bulges of spiral galaxies, with a focus on their abundances and abundance rati os. I conclude with a list of continui ng difcu lties in the modelli ng that complic ate the interpretation of integrated spectra as well as a look ahead to new methods and new observations. 1 .1 I ntrod uct ion The reviews presented in this volume demonstrate that the nucleosynthetic history of the Milky Way and its satellites can now be probed in exquisite detail, revealing a wealth of information about the processes by which our own Gala xy and its neighbors have formed. Such star-by-star analysis of the abundances of distant globular clusters and distant and/or dense galaxies is however currently beyond the reach of current telescopes. Although this situation might change with the advent of overwhelmingly large telescopes of the 30–100m class with high-precision adaptive optics systems, during the 20th Century and at the be- ginning of the 21st, we have been limited to studying the integrated stellar populations of distant globular clusters and galaxies. In this review, I will discuss spectroscopic techniques for determining abundances from the integrated light of galaxies and globular clusters. I will begin with a discussion of the ingredients of the models required to interpret the integrated-light spectra, the calibration of those models, and a few of their their pitfalls. I will then discuss the abundances determined from integrated light spectroscopy of globular clusters in our Galaxy, the Local Group, and the globular cluster systems of early-type galaxies. I will then consider the abundances of nearby early-type galaxies and the bulges of early-type spirals determined from integrated- light spectroscopy, including recent results on abundance anomalies in these systems. Al- though I will focus on deriving abundances from optical spectra, these results necessarily depend on the ages of the systems (through the age–metallicity degeneracy, § 1.2.1), and so I must briey discuss the ages of these syst ems. Final ly , I will summarize the curren t 1

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