Intermediate Mass Black Hole Induced Quenching of Mass Segregation in Star Clusters

TL;DR

This study uses direct N-body simulations to show that intermediate-mass black holes in globular clusters suppress mass segregation, providing a potential observational signature detectable with high-resolution imaging like HST.

Contribution

The paper introduces a novel observational method to detect IMBHs in globular clusters by analyzing the radial variation of stellar mass, based on extensive N-body simulations.

Findings

IMBHs quench mass segregation in star clusters.

Radial variation of average stellar mass is modest in clusters with IMBHs.

High-resolution imaging can identify IMBH candidates by measuring mass distribution.

Abstract

In many theoretical scenarios it is expected that intermediate-mass black holes (IMBHs, with masses M ~ 100-10000 solar masses) reside at the centers of some globular clusters. However, observational evidence for their existence is limited. Several previous numerical investigations have focused on the impact of an IMBH on the cluster dynamics or brightness profile. Here we instead present results from a large set of direct N-body simulations including single and binary stars. These show that there is a potentially more detectable IMBH signature, namely on the variation of the average stellar mass between the center and the half-light radius. We find that the existence of an IMBH quenches mass segregation and causes the average mass to exhibit only modest radial variation in collisionally relaxed star clusters. This differs from when there is no IMBH. To measure this observationally requires high resolution imaging at the level of that already available from the Hubble Space Telescope (HST) for the cores of a large sample of galactic globular clusters. With a modest additional investment of HST time to acquire fields around the half-light radius, it will be possible to identify the best candidate clusters to harbor an IMBH. This test can be applied only to globulars with a half-light relaxation time less than or equal to 1 Gyr, which is required to guarantee efficient energy equipartition due to two-body relaxation.