2023/07/10 by Manuel Arca Sedda, Albrecht Kamlah, Sedda, Manuel Arca +11 · 3 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2307.04806
openalex publication_date 2023/07/10 · openalex created_date 2023/07/13 · openalex updated_date 2026/07/30
The processes that govern the formation of intermediate-mass black holes (IMBHs) in dense stellar clusters are still unclear. Here, we discuss the role of stellar mergers, star-BH interactions and accretion, as well as BH binary (BBH) mergers in seeding and growing IMBHs in the Dragon-II simulation database, a suite of 19 direct N-body models representing dense clusters with up to 106 stars. Dragon-II IMBHs have typical masses of m\rm IMBH = (100-380) M_\odot and relatively large spins χ\rm IMBH > 0.6. We find a link between the IMBH formation mechanism and the cluster structure. In clusters denser than 3× 105 M_\odot pc-3, the collapse of massive star collision products represents the dominant IMBH formation process, leading to the formation of heavy IMBHs (m\rm IMBH > 200 M_\odot), possibly slowly rotating, that form over times <5 Myr and grow further via stellar accretion and mergers in just <30 Myr. BBH mergers are the dominant IMBH formation channel in less dense clusters, for which we find that the looser the cluster, the longer the formation time (10-300 Myr) and the larger the IMBH mass, although remaining within 200 M_\odot. Strong dynamical scatterings and relativistic recoil efficiently eject all IMBHs in Dragon-II clusters, suggesting that IMBHs in this type of cluster are unlikely to grow beyond a few 102 M_\odot.