How initial size governs core collapse in globular clusters
  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 H\'enon-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.
