Gravitational-wave kicks impact spins of black holes from hierarchical mergers

Understand

One proposed black hole formation channel involves hierarchical mergers, where black holes form through repeated binary mergers.

• Previous studies have shown that such black holes follow a near-universal spin distribution centered around 0.7.
• However, gravitational-wave kicks can eject remnants from their host environments, meaning only retained black holes can participate in subsequent mergers.
• We calculate the spin distribution of retained black holes in typical globular clusters, accounting for remnant kick velocities.