Abstract

Nuclear stellar clusters (NSCs) are the densest stellar systems in nature. The center of galaxies can host a NSC or a supermassive black hole (SMBH) they can also host both at the same time. The origin of SMBHs and their evolution is not clear; here we present a new scenario where runaway collisions in a nuclear stellar cluster are a mechanism for the formation of supermassive black holes. The stellar dynamics in the cluster include close encounters of stars that usually occur at high speed in the core due to the deep gravitational potential. Sometimes after these encounters, some stars can be ejected from the system with some kinetic energy, triggering a redistribution of the energy producing a core collapse, and causing one object to experience almost all collisions, becoming very massive. Our simulations show a black hole formation efficiency of 14-33% after 1 Myr of evolution. Our stellar systems show that the formation of a supermassive black hole is possible through collisions in a nuclear stellar cluster.