The growth of intermediate mass black holes through tidal captures and tidal disruption events

Francesco Paolo Rizzuto*, Thorsten Naab, Antti Rantala, Peter H. Johansson, Jeremiah P. Ostriker, Nicholas C. Stone, Shihong Liao, Dimitrios Irodotou

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

We present N-body simulations, including post-Newtonian dynamics, of dense clusters of low-mass stars harbouring central black holes (BHs) with initial masses of 50, 300, and 2000 M. The models are evolved with the N-body code BIFROST to investigate the possible formation and growth of massive BHs by the tidal capture of stars and tidal disruption events (TDEs). We model star–BH tidal interactions using a velocity-dependent drag force, which causes orbital energy and angular momentum loss near the BH. About ∼20–30 per cent of the stars within the spheres of influence of the black holes form Bahcall–Wolf cusps and prevent the systems from core collapse. Within the first 40 Myr of evolution, the systems experience 500–1300 TDEs, depending on the initial cluster structure. Most (>95 per cent) of the TDEs originate from stars in the Bahcall–Wolf cusp. We derive an analytical formula for the TDE rate as a function of the central BH mass, density, and velocity dispersion of the clusters (N∙TDE ∝ MBHρσ−3). We find that TDEs can lead a 300 M BH to reach ∼ 7000 M within a Gyr. This indicates that TDEs can drive the formation and growth of massive BHs in sufficiently dense environments, which might be present in the central regions of nuclear star clusters.

Original languageAmerican English
Pages (from-to)2930-2948
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Volume521
Issue number2
DOIs
StatePublished - 1 May 2023

Bibliographical note

Funding Information:
We thank the referee for the insightful comments, who enhanced the quality of this work. FPR, PHJ, SL, and DI acknowledge the support by the European Research Council via ERC Consolidator Grant KETJU (no. 818930). PHJ also acknowledges the support of the Academy of Finland grant 339127. TN acknowledges support from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC-2094 – 390783311 from the DFG Cluster of Excellence’ORIGINS’. The simulations have been carried out with the Ampere GPU system of the MPI for Astrophysics cluster ‘Freya’ hosted by the Max Planck Computing and Data facility. This study used also facilities hosted by the CSC – IT Centre for Science, Finland.

Publisher Copyright:
© 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.

Keywords

  • black hole mergers
  • galaxies: kinematics and dynamics
  • galaxies: nuclei
  • methods: numerical
  • quasars: supermassive black holes

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