Counter-Rotation and Slow Precession in Aligned Eccentric Nuclear Disks due to Gravitational Wave Recoil Kicks

TL;DR

This paper uses N-body simulations to show that gravitational wave recoil kicks can produce counter-rotating eccentric disks around supermassive black holes, explaining observed slow precession and increased stellar disruption rates.

Contribution

It demonstrates that gravitational wave recoil can create stable, counter-rotating eccentric disks with specific dynamical properties, a novel explanation for observed phenomena in galactic nuclei.

Findings

Counter-rotation fraction increases with recoil kick amplitude.

Disks with significant counter-rotation are more stable and eccentric.

Higher counter-rotation correlates with increased stellar tidal disruption rates.

Abstract

The M31 nucleus contains a supermassive black hole embedded in a massive stellar disk of apsidally-aligned eccentric orbits. It has recently been shown that this disk is slowly precessing at a rate consistent with zero. Here we demonstrate using N-body methods that apsidally-aligned eccentric disks can form with a significant (~0.5) fraction of orbits counter-rotating as the result of a gravitational wave recoil kick of merging supermassive black holes. Higher amplitude kicks map to a larger retrograde fraction in the surrounding stellar population which in turns results in slow precession. We furthermore show that disks with significant counter-rotation are more stable (that is, apsidal-alignment is most pronounced and long lasting), more eccentric, and have the highest rates of stars entering the black hole's tidal disruption radius