Mass and spin evolution of quasars and binary black hole mergers in globular clusters

Quasars are extremely luminous objects in the universe powered by supermassive black holes. The observed high masses of quasars at high redshift is an interesting subject to study to know how these objects generate such a high mass within so short time period after the Big Bang. It is also interesting to know what will be the spins of these objects and how these masses and spins evolve with time. In this work, we have worked on the time evolution of mass and spin of the quasars including different processes like accretion, stellar capture, mergers, and Blandford-Znajek effect. We discuss the importance of different growth channels and study the impact of this evolution on galaxy properties through the M-sigma relation.

A significant population of black hole (BH) binaries merging within a Hubble time can be produced by dynamical processes inside dense star clusters similar in properties to the globular clusters (GCs). Mergers may happen inside the GCs as well as outside if the BHs are ejected before merging. Even the in-cluster mergers may be ejected from the host cluster through large kicks eventually populating the halo or the bulge or even outside the galaxy. Using semi-analytic and numerical calculations we constrain the final positions of merging binary BHs depending on the orbital properties of their host GCs.