Abstract
Intermediate-mass black holes (IMBHs) are believed to be the missing link between the supermassive black holes (BHs) found at the centers of massive galaxies and BHs formed through stellar core collapse. One of the proposed mechanisms for their formation is a collisional runaway process in high-density young star clusters, where an unusually massive object forms through repeated stellar collisions and mergers, eventually collapsing to form an IMBH. This seed IMBH could then grow further through binary mergers with other stellar-mass BHs. Here we investigate the gravitational-wave (GW) signals produced during these later IMBH-BH mergers. We use a state-of-the-art semi-analytic approach to study the stellar dynamics and to characterize the rates and properties of IMBH-BH mergers. We also study the prospects for detection of these mergers by current and future GW observatories, both space-based (LISA) and ground-based (LIGO Voyager, Einstein Telescope, and Cosmic Explorer). We find that most of the merger signals could be detected, with some of them being multiband sources. Therefore, GWs represent a unique tool to test the collisional runaway scenario and to constrain the population of dynamically assembled IMBHs.
| Original language | English (US) |
|---|---|
| Article number | 191 |
| Journal | Astronomical Journal |
| Volume | 167 |
| Issue number | 5 |
| DOIs | |
| State | Published - May 1 2024 |
Funding
R.A.P. acknowledges support from the Student Experiential Learning Fund and the Undergraduate Advising and Research at Dartmouth College. This work was supported by NASA grant 80NSSC21K1722 and NSF grant AST-2108624 at Northwestern University (to G.F. and F.A.R.). We thank Miguel Angel Martinez and Quinn O. Casey for insightful discussions. R.A.P. was a summer student in the CIERA Summer REU program directed by Dr. Aaron Geller and supported by NSF grant AST-2149425. 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. Much of this research was carried out at Evanston, IL, which is home to the Potawatomi, Odawa, and Ojibwe Tribes, also known as the Niswimishkodewinan, an alliance of Anishinaabeg peoples.
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science