Rates of capture of stars by supermassive black holes in non-spherical galactic nuclei

TL;DR

This paper investigates how the shape of galactic nuclei affects the rate at which supermassive black holes capture stars, revealing that non-spherical geometries significantly increase capture rates especially for more massive black holes.

Contribution

The study introduces a new simulation method to distinguish collisional and collisionless processes influencing star capture rates in non-spherical galactic nuclei.

Findings

Non-spherical nuclei significantly increase star capture rates.

Modest triaxiality can sustain capture rates at a few percent of black hole mass per Hubble time.

Capture rate enhancement is substantial for black holes over 10^7 solar masses.

Abstract

We consider the problem of star consumption by supermassive black holes in non-spherical (axisymmetric, triaxial) galactic nuclei. We review the previous studies of the loss-cone problem and present a novel simulation method which allows to separate out the collisional (relaxation-related) and collisionless (related to non-conservation of angular momentum) processes and determine their relative importance for the capture rates in different geometries. We show that for black holes more massive than 10^7 Msun, the enhancement of capture rate in non-spherical galaxies is substantial, with even modest triaxiality being capable of keeping the capture rate at the level of few percent of black hole mass per Hubble time.