General relativistic quasi-spherical accretion in a dark matter halo

TL;DR

This study explores how dark matter influences spherical accretion onto supermassive black holes, revealing significant changes in flow properties and structure through relativistic hydrodynamics simulations.

Contribution

It introduces the first detailed general relativistic simulations of dark matter's impact on quasi-spherical accretion onto black holes.

Findings

Dark matter increases density, temperature, and pressure in accretion flows.

Presence of dark matter causes variations in radial velocity and can produce outflows.

Accretion dynamics are notably altered by dark matter, especially at high redshifts.

Abstract

Context. The Bondi spherical accretion solution has been used to model accretion onto compact objects in a variety of situations, from interpretation of observations to subgrid models in cosmological simulations. Aims. We aim to investigate how the presence of dark matter (DM) alters the dynamics and physical properties of accretion onto supermassive black holes on scales ranging from ~ 10 pc to the event horizon. Methods. In particular, we investigate Bondi-like accretion flows with zero and low specific angular momentum around supermassive black holes surrounded by dark-matter halos by performing 1D and 2.5D general relativistic hydrodynamics (GRHD) simulations using the black hole accretion code (BHAC). Results. We find notable differences in the dynamics and structure of spherical accretion flows in the presence of DM. The most significant effects include increases in density, temperature, and pressure, as well as variations in radial velocity both inside and outside the regions containing DM or even the production of outflow. Conclusions. This investigation provides valuable insights into the role of cosmological effects, particularly DM, in shaping the behavior of accretion flows and black holes (BHs). Our simulations may be directly applicable to model systems with a large black hole-to-halo mass ratio, which are expected to be found at very high redshifts.