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S. Zepf (Yale University)
Globular clusters are valuable fossils of the formation history of their parent galaxies because they provide an observable record of the physical conditions in their host galaxy at the time of their formation. I first review the strong evidence that globular clusters are being formed in ongoing gas-rich galaxy mergers and starbursts. I also review similarly strong evidence that elliptical galaxies typically possess two or more populations of globular clusters. This evidence comes from observations of the color distributions and now also of the kinematics of the cluster systems. Both of these observations confirm key predictions made previously by a model in which elliptical galaxies form by mergers and globular clusters form in these mergers. Within this framework, a number of critical issues remain to be addressed. One of these is to develop a better physical understanding of the merging and accretion that produced the observed episodic globular cluster formation. A second is to determine the role of dynamical processes in the evolution of globular cluster systems from the young systems observed in galaxy mergers to the old systems seen in the Milky Way and most ellipticals. A third area in which there is considerable uncertainty is a physical understanding of the formation of the globular clusters themselves. I show how some of these questions are being addressed through large spectroscopic surveys of extragalactic globular cluster systems, through detailed studies of the radii and luminosity functions of observed clusters, and through new models of globular cluster formation. These programs promise to ultimately lead to a better understanding of the formation of galaxies and their globular clusters.
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