Seeds to success: growing heavy black holes in dense star clusters

In this paper we investigate the formation of intermediate-mass black holes (IMBHs) in dense star clusters through stellar collisions and hierarchical binary black hole mergers, implementing B-POP simulations of 100 million black holes in young, globular and nuclear clusters. We investigate two IMBH seeding mechanisms (runaway and mild stellar collisions) and consider different cluster formation histories. We find that stellar collisions can be fundamental in sustaining IMBH formation in low-escape-velocity environments and reproduce potential IMBH observations in local globular clusters. We provide estimates of IMBH and intermediate-mass-ratio production efficiency for different environments and present an overview of the main ejection mechanisms. In addition, in the Discussion section we propose some interesting applications of our simulations to the study of IMBHs wandering in the galactic potential and the classification of IMBH host clusters.

Journal (A&A) · ADS · arXiv