The processes that go v ern 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 D RAGON -II simulation database, a suite of 19 direct N -body models representing dense clusters with up to 10 6 stars. D RAGON -II IMBHs have typical masses of m IMBH = (100–380) M  and relatively large spins χ IMBH > 0.6. We find a link between the IMBH formation mechanism and the cluster structure. In clusters denser than 3 × 10 5 M  pc −3 , the collapse of massive star collision products represents the dominant IMBH formation process, leading to the formation of heavy IMBHs ( m IMBH > 200 M  ), possibly slowly rotating, that form o v er 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  . Strong dynamical scatterings and relativistic recoil efficiently eject all IMBHs in D RAGON -II clusters, suggesting that IMBHs in this type of cluster are unlikely to grow beyond a few 10 2 M  .
The dragon-II simulations – II. Formation mechanisms, mass, and spin of intermediate-mass black holes in star clusters with up to 1 million stars
Manuel Arca-Sedda
Investigation
;
2023-01-01
Abstract
The processes that go v ern 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 D RAGON -II simulation database, a suite of 19 direct N -body models representing dense clusters with up to 10 6 stars. D RAGON -II IMBHs have typical masses of m IMBH = (100–380) M and relatively large spins χ IMBH > 0.6. We find a link between the IMBH formation mechanism and the cluster structure. In clusters denser than 3 × 10 5 M pc −3 , the collapse of massive star collision products represents the dominant IMBH formation process, leading to the formation of heavy IMBHs ( m IMBH > 200 M ), possibly slowly rotating, that form o v er 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 . Strong dynamical scatterings and relativistic recoil efficiently eject all IMBHs in D RAGON -II clusters, suggesting that IMBHs in this type of cluster are unlikely to grow beyond a few 10 2 M .I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
