2025/10/04 by Askar, Abbas, Vergara, Marcelo C., Ali, Sohaib
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2510.03766
Dense star clusters are promising nurseries for the formation and growth of intermediate-mass black holes (IMBHs; ∼ 102-105 M\odot), with increasing observational evidence pointing to their presence in massive star clusters and stripped dwarf-galaxy nuclei. During the early evolution of compact clusters, massive stars can rapidly segregate to the center, where frequent collisions may trigger the runaway growth of a very massive star (VMS). This object can subsequently collapse to form an IMBH or merge with a stellar-mass black hole. We carried out direct N-body and Monte Carlo simulations of star clusters with initial core densities between 106 to 4× 108 M\odot pc-3 and total masses of 5.9× 105 and 1.3× 106 M\odot. These models show that IMBHs of 103-104 M\odot can form within ≤ 5 Myr through the runaway collision channel. At later times, the IMBHs continue to grow through mergers with black holes, stars, and compact remnants, providing predictions testable with future gravitational-wave and transient surveys.