Hierarchical binary black hole mergers in globular clusters: mass function and evolution with redshift

Understand

Hierarchical black hole (BH) mergers are one of the most straightforward mechanisms to produce BHs inside and above the pair-instability mass gap.

• Here, we investigate the impact of globular cluster (GC) evolution on hierarchical mergers, and we account for the uncertainties related to BH mass pairing functions on the predicted primary BH mass, mass ratio and spin distribution.
• We find that the evolution of the host GC quenches the hierarchical BH assembly already at the third generation, mainly due to cluster expansion powered by a central BH sub-system.
• Hierarchical mergers match the primary BH mass distribution from GW events for $m_1 > 50 \, \mathrm{M_{\odot}}$, regardless of the assumed BH pairing function.