Energy flows in thick accretion disks and their consequences for black hole feedback

TL;DR

This study investigates energy flows in thick accretion disks around black holes through 3D simulations, revealing feedback efficiencies and the impact of black hole rotation on energy extraction and distribution.

Contribution

It provides new insights into the energy feedback mechanisms of thick accretion disks, including the effects of black hole spin and the distribution of energy between outflows and radiation.

Findings

Feedback efficiency is about 3% for non-rotating black holes.

Rotating black holes extract additional rotational energy, increasing efficiency.

Outflows and radiation distribute energy over wide angles, impacting the environment.

Abstract

We study energy flows in geometrically thick accretion discs, both optically thick and thin, using general relativistic, three-dimensional simulations of black hole accretion flows. We find that for non-rotating black holes the efficiency of the total feedback from thick accretion discs is $3\%$ - roughly half of the thin disc efficiency. This amount of energy is ultimately distributed between outflow and radiation, the latter scaling weakly with the accretion rate for super-critical accretion rates, and returned to the interstellar medium. Accretion on to rotating black holes is more efficient because of the additional extraction of rotational energy. However, the jet component is collimated and likely to interact only weakly with the environment, whereas the outflow and radiation components cover a wide solid angle.