Supermassive Black Holes in Galactic Nuclei with Tidal Disruption of Stars: Paper II - Axisymmetric Nuclei

TL;DR

This study uses high-precision N-body simulations to analyze how axisymmetry in galactic nuclei influences the rate and origin of stellar tidal disruptions by supermassive black holes, revealing increased disruption rates and distinct orbital features.

Contribution

It provides the first detailed analysis of tidal disruption rates and orbital distributions in axisymmetric nuclei, highlighting the role of non-conserved angular momentum in enhancing disruption rates.

Findings

Higher tidal disruption rate in axisymmetric systems compared to spherical ones.

Bimodal angular distribution of disrupted stars near the black hole.

Presence of two families of regular orbits, short axis tube and saucer, explaining orbital features.

Abstract

Tidal Disruption of stars by supermassive central black holes from dense rotating star clusters is modelled by high-accuracy direct N-body simulation. As in a previous paper on spherical star clusters we study the time evolution of the stellar tidal disruption rate and the origin of tidally disrupted stars, now according to several classes of orbits which only occur in axisymmetric systems (short axis tube and saucer). Compared with that in spherical systems, we found a higher TD rate in axisymmetric systems. The enhancement can be explained by an enlarged loss-cone in phase space which is raised from the fact that total angular momentum $\bf J$ is not conserved. As in the case of spherical systems, the distribution of the last apocenter distance of tidally accreted stars peaks at the classical critical radius. However, the angular distribution of the origin of the accreted stars reveals interesting features. Inside the influence radius of the supermassive black hole the angular distribution of disrupted stars has a conspicuous bimodal structure with a local minimum near the equatorial plane. Outside the influence radius this dependence is weak. We show that the bimodal structure of orbital parameters can be explained by the presence of two families of regular orbits, namely short axis tube and saucer orbits. Also the consequences of our results for the loss cone in axisymmetric galactic nuclei are presented.