Journal article
Repeated mergers, mass-gap black holes, and formation of intermediate-mass black holes in dense massive star clusters
- Abstract:
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Current theoretical models predict a mass gap with a dearth of stellar black holes (BHs) between roughly 50 M⊙ and 100 M⊙, while above the range accessible through massive star evolution, intermediate-mass BHs (IMBHs) still remain elusive. Repeated mergers of binary BHs, detectable via gravitational-wave emission with the current LIGO/Virgo/Kagra interferometers and future detectors such as LISA or the Einstein Telescope, can form both mass-gap BHs and IMBHs. Here we explore the possibility that mass-gap BHs and IMBHs are born as a result of successive BH mergers in dense star clusters. In particular, nuclear star clusters at the centers of galaxies have deep enough potential wells to retain most of the BH merger products after they receive significant recoil kicks due to anisotropic emission of gravitational radiation. Using for the first time simulations that include full stellar evolution, we show that a massive stellar BH seed can easily grow to ∼103–104 M⊙ as a result of repeated mergers with other smaller BHs. We find that lowering the cluster metallicity leads to larger final BH masses. We also show that the growing BH spin tends to decrease in magnitude with the number of mergers so that a negative correlation exists between the final mass and spin of the resulting IMBHs. Assumptions about the birth spins of stellar BHs affect our results significantly, with low birth spins leading to the production of a larger population of massive BHs.
- Publication status:
- Published
- Peer review status:
- Peer reviewed
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- Files:
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(Preview, Version of record, pdf, 2.2MB, Terms of use)
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- Publisher copy:
- 10.3847/1538-4357/ac5026
Authors
- Publisher:
- American Astronomical Society
- Journal:
- Astrophysical Journal More from this journal
- Volume:
- 927
- Issue:
- 2
- Article number:
- 231
- Publication date:
- 2022-03-21
- Acceptance date:
- 2022-01-28
- DOI:
- EISSN:
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1538-4357
- ISSN:
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0004-637X
- Language:
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English
- Keywords:
- Pubs id:
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1249326
- Local pid:
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pubs:1249326
- Deposit date:
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2023-05-01
Terms of use
- Copyright holder:
- Fragione et al.
- Copyright date:
- 2022
- Rights statement:
- © 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
- Licence:
- CC Attribution (CC BY)
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