Biased globular cluster formation

Abstract

Observations of extragalactic globular cluster systems have revealed that the total number of globular clusters belonging to a given galaxy depends sensitively on both its morphological type and local environment. Elliptical galaxies generally possess many more globular clusters than do spiral galaxies, and those located in rich galaxy clusters have systematically higher globular cluster abundances than their counterparts in the field, with cD galaxies having the largest globular cluster populations of all. It is shown here that this dependence of globular cluster populations on galaxy type and environment can be readily explained as a consequence of the well-known statistical enhancement of rare high-density peaks in the primordial matter distribution, i.e. biased globular cluster formation. For plausible assumptions about the biasing process it is possible to reproduce the observed trends quite well. Biased formation may also explain why certain globular cluster properties, such as their luminosity function, appear to be universal.