Forming Globular Cluster Systems Semi - Analytically

We describe a scheme for the formation of globular cluster systems in early-type galaxies using a semi-analytic model of galaxy formation. Operating within a ΛCDM cosmology, we assume that metal-poor globular clusters are formed at high-redshift in pre-galactic fragments, and that the subsequent gas-rich merging of these fragments leads to the formation of metal-rich clusters. We compare our results with contemporary data, and look at the particular case of the globular cluster and stellar metallicity distribution function of the nearby elliptical Centaurus A. 1. GENERAL Globular clusters (GCs) are long-lived tracers star formation, ranging from ancient, metal-poor stellar populations (e.g., Galactic halo GCs) to young, solar-metallicity stellar populations created during interactions (e.g., Schweizer et al. 1996). Due to their relatively " simple " nature (they are idealised simple stellar populations), the ages and metallici-ties of GCs can in principle be unambiguously determined. Hence, the study of GC systems affords a unique insight into the formation histories of galaxies. We have investigated the formation of the GC systems of elliptical galaxies using the fiducial semi-analytic model of Cole et al. (2000). We (Beasley et al. 2002a) assume GC formation occurs in two modes; in pre-galactic fragments with GC formation truncated at high redshift, and during the dissipative merging of these fragments. With these assumptions, we produced 450 real-isations of elliptical galaxy GC systems of over a range of halo masses i.e. ,