Nonlinear Gravitational Recoil from the Mergers of Precessing Black-Hole Binaries

TL;DR

This study models nonlinear gravitational recoil effects in precessing black-hole mergers, revealing a new 'cross kick' phenomenon that significantly increases the likelihood of high-velocity black hole ejections from galaxies.

Contribution

It introduces a new nonlinear contribution, the 'cross kick', to gravitational recoil in precessing black-hole mergers, expanding understanding of recoil dynamics.

Findings

Discovery of the 'cross kick' effect that enhances recoil velocities.

Recoil velocities exceeding 2000 km/s are nearly doubled in probability.

Implications for black hole ejections and galaxy dynamics.

Abstract

We present results from an extensive study of 88 precessing, equal-mass black-hole binaries with large spins (83 with intrinsic spins of 0.8 and 5 with intrinsic spins of 0.9)and use these data to model new nonlinear contributions to the gravitational recoil imparted to the merged black hole. We find a new effect, the cross kick, that enhances the recoil for partially aligned binaries beyond the hangup kick effect. This has the consequence of increasing the probabilities of recoils larger than 2000 km/s by nearly a factor two, and, consequently, of black holes getting ejected from galaxies, as well as the observation of large differential redshifts/blueshifts in the cores of recently merged galaxies.