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Photograph of Ross Church

Ross Church

Senior lecturer

Photograph of Ross Church

Merger rates in primordial black hole clusters without initial binaries

Author

  • Valeriya Korol
  • Ilya Mandel
  • M. Coleman Miller
  • Ross P. Church
  • Melvyn B. Davies

Summary, in English

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.

Department/s

  • Lund Observatory
  • eSSENCE: The e-Science Collaboration

Publishing year

2020

Language

English

Pages

994-1000

Publication/Series

Monthly Notices of the Royal Astronomical Society

Volume

496

Issue

1

Document type

Journal article

Publisher

Oxford University Press

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • black hole mergers
  • cosmology: dark matter
  • gravitational waves

Status

Published

ISBN/ISSN/Other

  • ISSN: 0035-8711