Massive black hole binary inspiral and spin evolution in a cosmological framework

Understand

Massive black hole (MBH) binary inspiral time scales are uncertain, and their spins are even more poorly constrained.

• Spin misalignment, along with unequal mass ratios and spin magnitudes, introduces asymmetry in the gravitational radiation, which imparts a recoil kick to the merged MBH.
• Understanding how MBH binary spins evolve is crucial for determining their recoil velocities, their gravitational wave (GW) waveforms detectable with LISA, as well as their post-merger retention rate in galaxies and thus their subsequent merger rate.
• Here we present a novel study that introduces a sub-resolution model for gas- and GW-driven MBH binary spin evolution using a population of accreting MBHs from the Illustris cosmological hydrodynamics simulations.