Supermassive black holes coalescence mediated by massive perturbers: Implications for gravitational waves emission and nuclear cluster formation

Manuel Arca Sedda*, Peter Berczik, Roberto Capuzzo-Dolcetta, Giacomo Fragione, Margaryta Sobolenko, Rainer Spurzem

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

A large fraction of galactic nuclei is expected to host supermassive black hole binaries (BHB), likely formed during the early phase of galaxies assembly and merging. In this paper, we use a large set of state-of-art numerical models to investigate the interplay between a BHB and a massive star cluster (GCs) driven toward the galactic centre by dynamical friction. Varying the BHB mass and mass ratio and the GC orbit, we show that the reciprocal feedback exerted between GCs and the BHB shapes their global properties. We show that, at GC-to-BHB mass ratios above 0.1, the GC affects notably the BHB orbital evolution, possibly boosting its coalescence. This effect is maximized if the GC moves on a retrograde orbit, and for a nonequal mass BHB. We show that the GC debris dispersed around the galactic nucleus can lead to the formation of a nuclear cluster, depending on the BHB tidal field, and that the distribution of compact remnants resulting from the GC disruption can carry information about the BHB orbital properties. We find that red giant stars delivered by the spiralling GC can be disrupted at a rate of ~ (0.7 - 7) × 10-7 yr-1 for BHB masses ~107M·, while tens to hundreds of stars can be possibly observed in the galactic halo as high-velocity stars, with velocities up to ~2000 km s-1, depending on the BHB orbital properties.

Original languageEnglish (US)
Pages (from-to)520-542
Number of pages23
JournalMonthly Notices of the Royal Astronomical Society
Volume484
Issue number1
DOIs
StatePublished - Mar 21 2019
Externally publishedYes

Keywords

  • Black hole physics - gravitational waves - Galaxy
  • Centre - galaxies
  • General
  • Nuclei - galaxies
  • Star clusters

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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