Bondi-like Accretion Flow Dynamics: The Role of Gravitational Potential

TL;DR

This study extends classical spherical accretion models by including host galaxy gravitational potentials, revealing that dark matter significantly enhances accretion rates and influences flow structures around black holes.

Contribution

It introduces a modified accretion model incorporating stellar and dark matter potentials, showing their impact on flow dynamics and accretion rates in astrophysical contexts.

Findings

Dark matter increases accretion rates by over 100%.

Flow structures resemble Bondi accretion with low angular momentum.

Gravitational potential of host galaxies critically affects accretion dynamics.

Abstract

The formation of massive black holes and their coevolution with host galaxies are pivotal areas of modern astrophysics. Spherical accretion onto a central point mass serves as a foundational framework in cosmological simulations, semi-analytical models, and observational studies. In this paper, we extend the classical spherical accretion model by incorporating the gravitational potential of host galaxies, including contributions from stellar components and dark matter halos. Numerical solutions spanning scales from parsecs down to ~ 10 r_s reveal that the flow structure is highly sensitive to the mass and size of the dark matter halo. Adding a small amount of angular momentum to the accreting gas demonstrates that such flows resemble spherical Bondi accretion, with mass accretion rates converging toward the Bondi rate. We find that the low angular momentum flow resembles the spherical Bondi flow, and its mass accretion rate approaches the Bondi accretion rate. Remarkably, due to the presence of dark matter, the mass accretion rate increases by more than ~ %100 compared to analogous hydrodynamic solutions without dark matter. These findings underscore the critical role of stellar and dark matter gravitational potentials in shaping the dynamics and accretion rates of quasi-spherical flows, providing new insights into astrophysical accretion processes.