Stellar Death and Black-Hole Mergers in galactic nuclei

Abstract

The dynamical and hydrodynamical evolution of stars and stellar remnants is greatly affected by the dense galactic nuclei (GN) environment. We explore the complex interplay of several physical processes that shape the properties, rates and environments of nuclear transients and black hole (BH) mergers and gravitational-wave (GW) events: We show how stellar dynamics shape the rate and properties of stellar BH mergers, extreme mass ratio inspiral (EMRI) and tidal disruption events (TDE), and its feedback on star formation history in the galactic centre. For active galactic nuclei (AGN), we study how the presence of an accretion disc modified the lightcurves of exploding supernovae and their relation to other nuclear transients. Finally, we examine in detail the torques in AGN discs that drive BH's radial migration. We find that thermal torques greatly alter the existence and nature of migration traps in AGN discs, which are believed to be responsible for massive hierarchical GW mergers. We explore the parameters space and draw conclusions on GW mergers in the LIGO band and EMRI in the LISA band.