The origin of the black hole offset in M31

TL;DR

This study uses advanced GPU N-body simulations to show that a satellite galaxy's infall can naturally cause the observed small offset of the black hole in M31, matching observational constraints.

Contribution

First demonstration that satellite infall explains the black hole offset in M31 using high-resolution GPU N-body simulations.

Findings

Satellite infall causes black hole offset via dynamical friction.

Black hole reaches maximum offset after first pericentric passage.

Black hole sinks back to center, ending with a sub-parsec offset.

Abstract

Using state-of-the-art high-resolution fully GPU N-body simulations, we demonstrate for the first time that the infall of a dark matter rich satellite naturally explains a present black hole offset by sub-parsecs in M31. Observational data of the tidal features provide stringent constraints on the initial conditions of our simulations. The heating of the central region of M31 by the satellite via dynamical friction entails a significant black hole offset after the first pericentric passage. After having reached its maximum offset, the massive black hole sinks towards the M31 centre due to dynamical friction and it is determined to be offset by sub-parsecs as derived by observations.