Building Massive Black Holes in Young Star Clusters

A variety of evidence suggests the majority of stars are born in stellar cluster or associations. For the most massive young stellar clusters (that may be similar to the progenitors of the old globular clusters observed at present in the Milky Way), dynamical interactions play a crucial role in shaping the properties of stars and, ultimately, the compact objects formed. In this talk I will discuss the dynamics of massive stars and black holes in young stellar clusters (ages less than 10-100 Myr). Informed by results from realistic N-body simulations, I will address a number of physical processes including the formation of very massive stars through runaway stellar collisions, the potential collapse of very massive stars into intermediate-mass black holes, as well as black hole growth through accretion of ambient gas and/or through successive mergers with other black holes. Additionally, I will describe the key (uncertain) properties of young clusters at birth that play an essential role in the features and event rates of these various processes. Finally, I will discuss the role of young star clusters (and old star clusters) in the dynamical formation of binary black hole mergers that may be similar to those observed as gravitational wave sources by LIGO/Virgo.