Monte Carlo Simulations of Globular Cluster Evolution. VI. The Influence of an Intermediate Mass Black Hole

TL;DR

This study uses Monte Carlo simulations to explore how an intermediate-mass black hole affects globular cluster structure, stellar disruption rates, and observable properties, comparing results with other methods and observations.

Contribution

It introduces a Monte Carlo approach that models realistic cluster dynamics with stellar evolution and mass spectrum, aligning well with N-body results and providing detailed observational comparisons.

Findings

Good agreement with N-body simulations on cluster structure and evolution.

Discrepancies in stellar disruption rates due to IMBH wandering motion.

Models with IMBH match observed surface brightness profiles of NGC 5694.

Abstract

We present results of a series of Monte Carlo simulations investigating the imprint of a central intermediate-mass black hole (IMBH) on the structure of a globular cluster. We investigate the three-dimensional and projected density profiles, and stellar disruption rates for idealized as well as realistic cluster models, taking into account a stellar mass spectrum and stellar evolution, and allowing for a larger, more realistic, number of stars than was previously possible with direct N-body methods. We compare our results to other N-body and Fokker-Planck simulations published previously. We find, in general, very good agreement for the overall cluster structure and dynamical evolution between direct N-body simulations and our Monte Carlo simulations. Significant differences exist in the number of stars that are tidally disrupted by the IMBH, which is most likely an effect of the wandering motion of the IMBH, not included in the Monte Carlo scheme. These differences, however, are negligible for the final IMBH masses in realistic cluster models as the disruption rates are generally much lower than for single-mass clusters. As a direct comparison to observations we construct a detailed model for the cluster NGC 5694, which is known to possess a central surface brightness cusp consistent with the presence of an IMBH. We find that not only the inner slope but also the outer part of the surface brightness profile agree well with observations. However, there is only a slight preference for models harboring an IMBH compared to models without.