Presentation #201.09 in the session Star Clusters and Associations — iPoster Session.
For massive stars, the dynamical interactions facilitated by the high densities in dense star cluster cores can lead to large numbers of stellar collisions and unique stellar evolution pathways not possible for stars evolving in isolation. For example, recent studies have shown that dynamically-mediated massive star collisions that occur within the first few Myr of a young star cluster may lead to the formation of massive stars that, upon stellar collapse, may create black holes within the proposed “upper mass gap” between roughly 40 and 120 solar masses expected from (pulsational) pair-instability supernovae. Formation of these massive black holes in clusters has key implications for the massive black holes detected as gravitational wave sources by LIGO, such as GW190521. Here we create hundreds of N-body cluster models that cover a wide range of star cluster properties to study the effects of stellar collisions/mergers on black hole formation. Furthermore, we study how various cluster properties, such as metallicity, affect these processes, and find that as many as 14 mass-gap black holes can form in a single cluster through massive star collisions/mergers. We also examine the potential electromagnetic transients, such as pair instability supernovae (PISNe), and make predictions for the rates of these transients in the local universe and how these rates depend on cluster properties. We find that PISNe occur at a volumetric rate of ~0.2 Gpc-3 yr-1 at z = 0, and ~20 Gpc-3 yr-1 at z = 1, while collapsars are formed at a rate of ~60 Gpc-3 yr-1 at z = 0, and ~1000 Gpc-3 yr-1 at z = 1.