The Formation of Intermediate-mass Black Holes in Galactic Nuclei

Sanaea C. Rose*, Smadar Naoz, Re'Em Sari, Itai Linial

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

Most stellar evolution models predict that black holes (BHs) should not exist above approximately 50-70 M ⊙, the lower limit of the pair-instability mass gap. However, recent LIGO/Virgo detections indicate the existence of BHs with masses at and above this threshold. We suggest that massive BHs, including intermediate-mass BHs (IMBHs), can form in galactic nuclei through collisions between stellar-mass BHs and the surrounding main-sequence stars. Considering dynamical processes such as collisions, mass segregation, and relaxation, we find that this channel can be quite efficient, forming IMBHs as massive as 104 M o˙. This upper limit assumes that (1) the BHs accrete a substantial fraction of the stellar mass captured during each collision and (2) that the rate at which new stars are introduced into the region near the SMBH is high enough to offset depletion by stellar disruptions and star-star collisions. We discuss deviations from these key assumptions in the text. Our results suggest that BHs in the pair-instability mass gap and IMBHs may be ubiquitous in galactic centers. This formation channel has implications for observations. Collisions between stars and BHs can produce electromagnetic signatures, for example, from X-ray binaries and tidal disruption events. Additionally, formed through this channel, both BHs in the mass gap and IMBHs can merge with the SMBHs at the center of a galactic nucleus through gravitational waves. These gravitational-wave events are extreme- and intermediate-mass ratio inspirals.

Original languageAmerican English
Article numberL22
JournalAstrophysical Journal Letters
Volume929
Issue number2
DOIs
StatePublished - 1 Apr 2022

Bibliographical note

Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.

Fingerprint

Dive into the research topics of 'The Formation of Intermediate-mass Black Holes in Galactic Nuclei'. Together they form a unique fingerprint.

Cite this