An Overview of Globular Cluster Systems in Distant Galaxies

Information is currently available for globular cluster systems in almost 50 galaxies from the Milky Way to the Coma Cluster. The observed features of these systems are reviewed, with emphasis on (a) their total populations (specific frequencies), (b) spatial structures compared with the underlying halo light, (c) photometric characteristics (luminosity function and metallicity). The combined evidence suggests strongly that globular clusters are likely to have formed in a rather sharply defined epoch clearly before the bulk of the halo field stars, and that this epoch was more active in E galaxies, especially those in rich environments. Finally, the special role of the supergiant E's at the centers of rich galaxy clusters is reviewed.