MOCCA-SURVEY Database I: Galactic Globular Clusters Harbouring a Black Hole Subsystem

TL;DR

This study identifies 29 Galactic globular clusters likely hosting black hole subsystems by analyzing observational data and theoretical models, providing estimates of their properties and potential black hole populations.

Contribution

The paper introduces a method to identify globular clusters with black hole subsystems using observational data and scaling relations, building on previous simulation results.

Findings

29 GCs potentially harboring black hole subsystems identified

Estimated properties of black hole subsystems in these GCs provided

Additional clusters possibly containing significant black hole populations

Abstract

There have been increasing theoretical speculations and observational indications that certain globular clusters (GCs) could contain a sizeable population of stellar mass black holes (BHs). In this paper, we shortlist at least 29 Galactic GCs that could be hosting a subsystem of BHs (BHS). In a companion paper, we analysed results from a wide array of GC models (simulated with the MOCCA code for cluster simulations) that retained few tens to several hundreds of BHs at 12 Gyr and showed that the properties of the BHS in those GCs correlate with the GC's observable properties. Building on those results, we use available observational properties of 140 Galactic GCs to identify 29 GCs that could potentially be harbouring up to a few hundreds of BHs. Utilizing observational properties and theoretical scaling relations, we estimate the density, size and mass of the BHS in these GCs. We also calculate the total number of BHs and the fraction of BHs contained in a binary system for our shortlisted Galactic GCs. Additionally, we mention other Galactic GCs that could also contain significant number of single BHs or BHs in binary systems.