Supermassive recoil velocities for binary black-hole mergers with antialigned spins

TL;DR

This paper demonstrates that binary black hole mergers with anti-aligned spins can produce recoil velocities exceeding 2500 km/s, significantly higher than previous predictions, impacting models of black hole and galaxy evolution.

Contribution

It provides the first evidence that anti-aligned spins in equal-mass binaries can generate recoil velocities over 2500 km/s, challenging prior estimates.

Findings

Recoil velocities of at least 2500 km/s are possible.

Anti-aligned spins can produce higher kicks than previously predicted.

Implications for black hole retention in galaxies.

Abstract

Recent calculations of the recoil velocity in binary black hole mergers have found the kick velocity to be of the order of a few hundred km/s in the case of non-spinning binaries and about $500 $km/s in the case of spinning configurations, and have lead to predictions of a maximum kick of up to $1300 $km/s. We test these predictions and demonstrate that kick velocities of at least $2500 $km/s are possible for equal-mass binaries with anti-aligned spins in the orbital plane. Kicks of that magnitude are likely to have significant repercussions for models of black-hole formation, the population of intergalactic black holes and the structure of host galaxies.