Non-isotropic feedback from accreting spinning black holes

TL;DR

This paper introduces a new momentum-driven AGN feedback model in hydrodynamic simulations, demonstrating that outflow shape remains conical with orientation influenced by the circumnuclear disc, affecting outflow velocity.

Contribution

The study develops a novel bi-conical feedback model with adjustable orientation based on BH spin or gas angular momentum, improving realism in AGN feedback simulations.

Findings

Outflow shape remains conical regardless of orientation.

Outflow orientation is influenced by interaction with the circumnuclear disc.

Outflow velocity varies significantly depending on disc interaction.

Abstract

Active galactic nuclei (AGN) are massive black holes (BHs) caught in the act of accreting gas at the centre of their host galaxies. Part of the accreting mass is converted to energy and released into the surrounding medium, in a process loosely referred to as AGN feedback. Most numerical simulations include AGN feedback as a sub-grid model, wherein energy or momentum (or both) is coupled to the nearby gas. In this work, we implement a new momentum-driven model in the hydrodynamics code GIZMO, in which accretion from large scales is mediated by a sub-grid accretion disc model, and gas particles are stochastically kicked over a bi-conical region, to mimic observed kinetic winds. The feedback cone's axis can be set either parallel to the angular momentum of the gas surrounding the BH or to the BH spin direction, which is self-consistently evolved within the accretion-disc model. Using a circumnuclear disc (CND) as a test bed, we find that (i) the conical shape of the outflow is always visible and is weakly dependent on the launching orientation and aperture, resulting in comparable mass inflows and outflows; (ii) the cone's orientation is also similar amongst our tests, and it is not always the same as the initial value, due to the interaction with the CND playing a crucial role in shaping the outflow; and (iii) the velocity of the outflow, instead, differs and strongly depends on the interplay with the CND.