Star-disc interaction in galactic nuclei: formation of a central stellar disc

TL;DR

This study uses high-resolution N-body simulations to explore how an accretion disc influences stellar dynamics in galactic nuclei, leading to the formation of a central stellar disc around a supermassive black hole.

Contribution

It demonstrates the formation of a stellar disc due to star-disc interactions and quantifies its properties and formation timescales in active galactic nuclei.

Findings

Stellar disc forms in the central region of the nuclear stellar cluster.

The migration time through the accretion disc is about 3% of the NSC's half-mass relaxation time.

The stellar disc's mass is approximately 0.7% of the black hole's influence radius.

Abstract

We perform high resolution direct $N$-body simulations to study the effect of an accretion disc on stellar dynamics in an active galactic nucleus (AGN). We show that the interaction of the nuclear stellar cluster (NSC) with the gaseous disc (AD) leads to formation of a stellar disc in the central part of the NSC. The accretion of stars from the stellar disc onto the super-massive black hole is balanced by the capture of stars from the NSC into the stellar disc, yielding a stationary density profile. We derive the migration time through the AD to be 3\% of the half-mass relaxation time of the NSC. The mass and size of the stellar disc are 0.7\% of the mass and 5\% of the influence radius of the super-massive black hole. An AD lifetime shorter than the migration time would result in a less massive nuclear stellar disc. The detection of such a stellar disc could point to past activity of the hosting galactic nucleus.