Speaker
Description
Population III (Pop. III) stars are promising progenitors of intermediate-mass black holes (IMBHs) due to their reduced mass loss and top-heavy initial mass function. If these stars formed predominantly in star clusters, they could efficiently produce IMBHs up to $10^4\,\rm M_{\odot}$ and generate massive binary systems that eventually merge. In this talk, I will present results from two complementary approaches: semi-analytical models, and direct N-body simulations of Pop. III star clusters informed by cosmological simulations. By exploring a broad range of cluster properties, stellar evolution prescriptions, and orbital parameter distributions, I will show that the majority of binary black hole (BBH) mergers originating from Pop. III star clusters involve primaries above the upper mass gap. I will then investigate the detectability of these mergers across cosmic time, highlighting their potential contribution to future gravitational-wave observations with the Einstein Telescope. Finally, I will discuss the dominant dynamical channels leading to IMBH formation in Pop. III star clusters at $z\sim20$, and assess their possible role as seeds of the supermassive black holes observed at high redshift.