2008 Supplement: Frascati Workshop 2007 / Beckman

The Role of Mergers in Galaxy Evolution

J. Beckman, C. Carretero, A. Vazdekis

Abstract

In the last decade the importance of mergers in the evolution of
galaxies has become evident. In this paper we illustrate this importance
by showing examples of merging galaxies, both local and at increasing
redshift. However before getting carried away by the charms of the
hierarchical model in which large galaxies have been built up by
successive mergers of smaller objects, it is worth looking at what
stellar population synthesis can tell us. Here I show that, using
indices which allow us to separate the effects of metallicity and age on
the spectra of the stellar populations of galaxies, we can show that the
most massive galaxies have the oldest stellar populations, an effect
which is enhanced within galaxy clusters and is maximized within the
most massive clusters. These measurements imply that a model where
mergers (even ``dry" mergers) are the main driver for galaxy evolution
cannot be giving us anything like a valid picture. The role of mergers
must be considerably more subtle than one would infer from the standard
semi-analytic models of galaxy evolution within a cosmological
framework.

Keywords


Galaxies mergers chemical diagnostics

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