Multi-scale simulations of black hole accretion in barred galaxies

Self-gravitating disk models

¹ Institute for Theoretical Physics and Astrophysics, Kiel Astrophysics, Christian-Albrechts-University Kiel, Leibnizstraße 15, 24118 Kiel, Germany
² Hamburger Sternwarte, Universität Hamburg, Gojensbergweg 112, 21029 Hamburg, Germany
e-mail: manuel.jung@hs.uni-hamburg.de
³ Steward Observatory, The University of Arizona, Tucson AZ 85721, USA

Received: 1 August 2017
Accepted: 18 February 2018

Abstract

Due to the non-axisymmetric potential of the central bar, in addition to their characteristic arms and bar, barred spiral galaxies form a variety of structures within the thin gas disk, such as nuclear rings, inner spirals, and dust lanes. These structures in the inner kiloparsec are extremely important in order to explain and understand the rate of black hole feeding. The aim of this work is to investigate the influence of stellar bars in spiral galaxies on the thin self-gravitating gas disk. We focus on the accretion of gas onto the central supermassive black hole and its time-dependent evolution. We conducted multi-scale simulations simultaneously resolving the galactic disk and the accretion disk around the central black hole. In all the simulations we varied the initial gas disk mass. As an additional parameter we chose either the gas temperature for isothermal simulations or the cooling timescale for non-isothermal simulations. Accretion was either driven by a gravitationally unstable or clumpy accretion disk or by energy dissipation in strong shocks. Most of the simulations show a strong dependence of the accretion rate at the outer boundary of the central accretion disk (r < 300 pc) on the gas flow at kiloparsec scales. The final black hole masses reach up to ~10⁹ M_⊙ after 1.6 Gyr. Our models show the expected influence of the Eddington limit and a decline in growth rate at the corresponding sub-Eddington limit.