Resolving Gas Dynamics in the Circumnuclear Region of a Disk Galaxy in a Cosmological Simulation

TL;DR

This study uses high-resolution hydrodynamic simulations to explore gas dynamics and instabilities in the circumnuclear region of a galaxy, shedding light on black hole growth mechanisms.

Contribution

It provides a detailed simulation of gas behavior from large scales down to the accretion disk, revealing the role of instabilities in angular momentum transport.

Findings

Gas density follows a r^-8/3 power-law profile.

Global instabilities facilitate angular momentum transport.

Circumnuclear disk turbulence supports accretion processes.

Abstract

Using a hydrodynamic adaptive mesh refinement code, we simulate the growth and evolution of a galaxy, which could potentially host a supermassive black hole, within a cosmological volume. Reaching a dynamical range in excess of 10 million, the simulation follows the evolution of the gas structure from super-galactic scales all the way down to the outer edge of the accretion disk. Here, we focus on global instabilities in the self-gravitating, cold, turbulence-supported, molecular gas disk at the center of the model galaxy, which provide a natural mechanism for angular momentum transport down to sub-pc scales. The gas density profile follows a power-law scaling as r^-8/3, consistent with an analytic description of turbulence in a quasi-stationary circumnuclear disk. We analyze the properties of the disk which contribute to the instabilities, and investigate the significance of instability for the galaxy's evolution and the growth of a supermassive black hole at the center.