Where Are Most of the Globular Clusters in Today's Universe?

TL;DR

This paper analyzes the distribution of globular clusters across galaxies, showing they are most common in galaxies around a characteristic luminosity and highlighting the dominance of blue, metal-poor clusters globally.

Contribution

It provides a quantitative model of globular cluster distribution across galaxy luminosities and reveals the predominance of blue clusters in the universe.

Findings

Globular clusters are most abundant in galaxies near luminosity L*.

Blue (metal-poor) GCs outnumber red (metal-rich) GCs by 4 to 1 globally.

The earliest galaxy formation favored the creation of dense star clusters.

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.