Modeling Dense Star Clusters in the Milky Way and Beyond with the CMC Cluster Catalog

Abstract

We present a set of 148 independent N -body simulations of globular clusters (GCs) computed using the code CMC (Cluster Monte Carlo). At an age of ∼ 10−13 Gyr, the resulting models cover nearly the full range of cluster properties exhibited by the Milky Way GCs, including total mass, core and half-light radii, metallicity, and galactocentric distance. We use our models to investigate the role that stellarmass black holes play in the process of core collapse. Furthermore, we study how dynamical interactions affect the formation and evolution of several important types of sources in GCs, including low-mass X-ray binaries, millisecond pulsars, blue stragglers, cataclysmic variables, Type Ia supernovae, calciumrich transients, and merging compact binaries. While our focus here is on old, low-metallicity GCs, our CMC simulations follow the evolution of clusters over a Hubble time, and they include a wide range of metallicities (up to solar), so that our results can also be used to study younger and higher-metallicity star clusters.2. METHODS 2.1. Summary of CMC

Merger rate of black hole binaries from globular clusters: Theoretical error bars and comparison to gravitational wave data from GWTC-2

“…Our value of ρ GC is larger than what was found by [18]: if we adopt their assumption of an average GC mass of 3 × 10 5 M ⊙ , we find that equation 2corresponds to a GC number density of n GC = 2.4 Mpc −3 , which is 3.3 times larger than their n GC = 0.72 Mpc −3 , but similar to the value used in [15] and [23]. Part of this difference is because we adopted a larger value of η: if we use their mild M h -dependent η from [39], we find n GC = 1.50 Mpc −3 , which corresponds to our lower error bar ⟨η⟩.…”

“…We now use a simplified analytical model to gain some physical insights on this result. From equation (23), the merger rate for in-cluster binaries is…”

“…Several recent studies only considered the contribution from clusters that have survived to the present day [e.g., 19,23]. These studies found that the present-day population of GCs produces BHB mergers at a local rate of ≈ 5 Gpc −3 yr −1 .…”

Black Hole Mergers from Hierarchical Triples in Dense Star Clusters

“…In Kremer et al (2020b), 148 cluster simulations 11 were produced, varying the total number of particles (single stars plus binaries; =Ń 2 10 5 , 4×10 5 , 8×10 5 ,1.6 10 6 , and 3.2 10 6 ), initial cluster virial radius…”

“…When this happens, only the eccentricity at the final passage through this value is shown. In addition to the KL mergers (solid black) and non-KL mergers (dashed black), also included are the few-body capture (solid orange), single-single capture (dashed orange), ejected (solid blue), and in-cluster (dashed blue) binary mergers from Kremer et al (2020b), along with results from Kremer et al (2019), which show eccentricities for field binaries (solid pink). As the few-body capture and single-single capture mergers form at frequencies above 0.01 Hz, they are not included in the bottom panel.…”