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Merger rates in primordial black hole clusters without initial binaries

Korol, Valeriya ; Mandel, Ilya ; Coleman Miller, M. ; Church, Ross P. LU orcid and Davies, Melvyn B. LU (2020) In Monthly Notices of the Royal Astronomical Society 496(1). p.994-1000
Abstract

Primordial black holes formed through the collapse of cosmological density fluctuations have been hypothesized as contributors to the dark matter content of the Universe. At the same time, their mergers could contribute to the recently observed population of gravitational-wave sources. We investigate the scenario in which primordial black holes form binaries at late times in the Universe. Specifically, we re-examine the mergers of primordial black holes in small clusters of ∼30 objects in the absence of initial binaries. Binaries form dynamically through Newtonian gravitational interactions. These binaries act as heat sources for the cluster, increasing the cluster's velocity dispersion, which inhibits direct mergers through... (More)

Primordial black holes formed through the collapse of cosmological density fluctuations have been hypothesized as contributors to the dark matter content of the Universe. At the same time, their mergers could contribute to the recently observed population of gravitational-wave sources. We investigate the scenario in which primordial black holes form binaries at late times in the Universe. Specifically, we re-examine the mergers of primordial black holes in small clusters of ∼30 objects in the absence of initial binaries. Binaries form dynamically through Newtonian gravitational interactions. These binaries act as heat sources for the cluster, increasing the cluster's velocity dispersion, which inhibits direct mergers through gravitational-wave two-body captures. Meanwhile, three-body encounters of tight binaries are too rare to tighten binaries sufficiently to allow them to merge through gravitational-wave emission. We conclude that in the absence of initial binaries, merger rates of primordial black holes in the considered scenario are at least an order of magnitude lower than previously suggested, which makes gravitational-wave detections of such sources improbable.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
black hole mergers, cosmology: dark matter, gravitational waves
in
Monthly Notices of the Royal Astronomical Society
volume
496
issue
1
pages
7 pages
publisher
Oxford University Press
external identifiers
  • scopus:85088587822
ISSN
0035-8711
DOI
10.1093/mnras/staa1644
language
English
LU publication?
yes
id
fbf41554-bbd4-4264-a5d4-69433706947d
date added to LUP
2020-08-05 09:10:56
date last changed
2024-04-17 13:15:51
@article{fbf41554-bbd4-4264-a5d4-69433706947d,
  abstract     = {{<p>Primordial black holes formed through the collapse of cosmological density fluctuations have been hypothesized as contributors to the dark matter content of the Universe. At the same time, their mergers could contribute to the recently observed population of gravitational-wave sources. We investigate the scenario in which primordial black holes form binaries at late times in the Universe. Specifically, we re-examine the mergers of primordial black holes in small clusters of ∼30 objects in the absence of initial binaries. Binaries form dynamically through Newtonian gravitational interactions. These binaries act as heat sources for the cluster, increasing the cluster's velocity dispersion, which inhibits direct mergers through gravitational-wave two-body captures. Meanwhile, three-body encounters of tight binaries are too rare to tighten binaries sufficiently to allow them to merge through gravitational-wave emission. We conclude that in the absence of initial binaries, merger rates of primordial black holes in the considered scenario are at least an order of magnitude lower than previously suggested, which makes gravitational-wave detections of such sources improbable.</p>}},
  author       = {{Korol, Valeriya and Mandel, Ilya and Coleman Miller, M. and Church, Ross P. and Davies, Melvyn B.}},
  issn         = {{0035-8711}},
  keywords     = {{black hole mergers; cosmology: dark matter; gravitational waves}},
  language     = {{eng}},
  number       = {{1}},
  pages        = {{994--1000}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{Merger rates in primordial black hole clusters without initial binaries}},
  url          = {{http://dx.doi.org/10.1093/mnras/staa1644}},
  doi          = {{10.1093/mnras/staa1644}},
  volume       = {{496}},
  year         = {{2020}},
}