Buchi neri in ammassi stellari giovani

Understanding the formation channels of binary black holes (BBHs) is one of the most urgent astrophysical questions raised by the results of the LIGO-Virgo collaboration (LVC). The aim of this Thesis is to understand what is the global effect of dynamics of young SCs on BHs, focusing on GW sources. I have interfaced the direct Nbody code Nbody6++GPU with the population synthesis code MOBSE. I have run 10^4 simulations of young SCs with 40% initial binary fraction, fractal initial conditions and different initial mass, metallicity and radius. I find that dynamics significantly affects the properties of merging BBHs in young SCs, favoring the formation and the merger of more massive BBHs (total mass up to∼140 Msun) and with smaller mass ratios (up to∼0.1) with respect to BBHs formed in isolation. Metallicity strongly affects the mass spectrum of BHs, BBHs and merging BBHs, which tend to be more massive in metal-poor SCs. Based on our simulations, the most massive LIGO–Virgo events (GW170729 and GW190521) and the first unequal-mass merger (GW190412) can only be explained by exchanged BBHs in metal-poor SCs. My simulations predicted that BHs in the pair instability (PI) mass gap can form via stellar mergers. We predict that∼5% of all BBH mergers detected by LIGO and Virgo at design sensitivity have at least one component in the PI mass gap. Intermediate mass black holes with mass up to ~440 Msun form in my simulations via the runaway collision mechanism.