WHERE ARE MOST OF THE GLOBULAR CLUSTERS IN TODAY’S UNIVERSE?

Abstract

The total number of globular clusters (GCs) in a galaxy rises continuously with the galaxy luminosity L , while the relative number of galaxies decreases with L following the Schechter function. The product of these two very nonlinear functions gives the relative number of GCs contained by all galaxies at a given L . It is shown that GCs, in this universal sense, are most commonly found in galaxies within a narrow range around L ⋆ . In addition, blue (metal-poor) GCs outnumber the red (metal-richer) ones globally by 4 to 1 when all galaxies are added, pointing to the conclusion that the earliest stages of galaxy formation were especially favorable to forming massive, dense star clusters.