The physics governing the upper truncation mass of the globular cluster mass function

Abstract

The mass function of globular cluster (GC) populations is a fundamental observable that encodes the physical conditions under which these massive stellar clusters formed and evolved. The high-mass end of star cluster mass functions are commonly described using a Schechter function, with an exponential truncation mass $M_{c,\ast }$. For the GC mass functions in the Virgo galaxy cluster, this truncation mass increases with galaxy mass ($M_{\ast }$). In this paper we fit Schechter mass functions to the GCs in the most massive galaxy group ($M_{200}=5.14\times 10^{13}{M}_{\odot }$) in the E-MOSAICS simulations. The fiducial cluster formation model in E-MOSAICS reproduces the observed trend of $M_{c,\ast }$ with $M_{\ast }$ for the Virgo cluster. We therefore examine the origin of the relation by fitting $M_{c,\ast }$ as a function of galaxy mass, with and without accounting for mass loss by two-body relaxation, tidal shocks and/or dynamical friction. In the absence of these mass-loss mechanisms, the $M_{c,\ast }$-$M_{\ast }$ relation is flat above $M_{\ast }>10^{10}{M}_{\odot }$. It is therefore the disruption of high-mass GCs in galaxies with $M_{\ast }\sim 10^{10}{M}_{\odot }$ that lowers the $M_{c,\ast }$ in these galaxies. High-mass GCs are able to survive in more massive galaxies, since there are more mergers to facilitate their redistribution to less-dense environments. The $M_{c,\ast }-M_{\ast }$ relation is therefore a consequence of both the formation conditions of massive star clusters and their environmentally-dependent disruption mechanisms.

Accepted to MNRAS

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