Globular clusters ( GCs ) in the Milky Way exhibit a well-observed bimodal distribution in core radii separating the so-called “ core-collapsed ” and “ non-core-collapsed ” clusters .
Here , we use our Hénon-type Monte Carlo code , CMC , to explore initial cluster parameters that map into this bimodality .
Remarkably , we find that by varying the initial size of clusters ( specified in our initial conditions in terms of the initial virial radius , r _ { v } ) within a relatively narrow range consistent with the measured radii of young star clusters in the local universe ( r _ { v } \approx 0.5 - 5 pc ) , our models reproduce the variety of present-day cluster properties .
Furthermore , we show that stellar-mass black holes ( BHs ) play an intimate role in this mapping from initial conditions to the present-day structural features of GCs .
We identify “ best-fit ” models for three GCs with known observed BH candidates , NGC 3201 , M22 , and M10 , and show that these clusters harbor populations of \sim 50 - 100 stellar-mass BHs at present .
As an alternative case , we also compare our models to the core-collapsed cluster NGC 6752 and show that this cluster likely contains few BHs at present .
Additionally , we explore the formation of BH binaries in GCs and demonstrate that these systems form naturally in our models in both detached and mass-transferring configurations with a variety of companion stellar types , including low-mass main sequence stars , white dwarfs , and sub-subgiants .