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 $L_{\star}$. 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.