Abstract
The existence of black holes (BHs) with masses in the range between stellar remnants and supermassive BHs has only recently become unambiguously established. GW190521, a gravitational wave signal detected by the LIGO/Virgo Collaboration, provides the first direct evidence for the existence of such intermediate-mass BHs (IMBHs). This event sparked and continues to fuel discussion on the possible formation channels for such massive BHs. As the detection revealed, IMBHs can form via binary mergers of BHs in the “upper mass gap” (≈40-120 M ⊙). Alternatively, IMBHs may form via the collapse of a very massive star formed through stellar collisions and mergers in dense star clusters. In this study, we explore the formation of IMBHs with masses between 120 and 500 M ⊙ in young, massive star clusters using state-of-the-art Cluster Monte Carlo models. We examine the evolution of IMBHs throughout their dynamical lifetimes, ending with their ejection from the parent cluster due to gravitational radiation recoil from BH mergers, or dynamical recoil kicks from few-body scattering encounters. We find that all of the IMBHs in our models are ejected from the host cluster within the first ∼500 Myr, indicating a low retention probability of IMBHs in this mass range for globular clusters today. We estimate the peak IMBH merger rate to be ≈ 2 Gpc − 3 yr − 1 at redshift z ≈ 2.
| Original language | English (US) |
|---|---|
| Article number | 131 |
| Journal | Astrophysical Journal |
| Volume | 940 |
| Issue number | 2 |
| DOIs | |
| State | Published - Dec 1 2022 |
Funding
This work was supported by NSF grant AST-2108624 and NASA grant 80NSSC22K0722. G.F. and F.A.R. acknowledge support from NASA grant 80NSSC21K1722. K.K. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-2001751. N.C.W. acknowledges support from the CIERA Riedel Family Graduate Fellowship. Support for M.Z. is provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51474.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. This research was supported in part through the computational resources and staff contributions provided for the Quest high performance computing facility at Northwestern University, which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology.
Keywords
- Binary stars
- Black holes
- Intermediate-mass black holes
- N-body simulations
- Stellar mergers
- Young star clusters
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science