Razieh
Ranjbar
School of Astronomy, Institute for Research in Fundamental Sciences (IPM)
Abstract
Recent observations of nearby low-luminosity active galactic nuclei (AGNs), in cases where the Bondi radius is resolved, have found accretion rates that are several orders of magnitude lower than those predicted by the classical Bondi model, as observed in M87, Sgr A*, and NGC 3115. Although supermassive black holes at galaxy centers are believed to evolve together with their host galaxies, how they interact across large scales remains a key challenge in understanding galaxy evolution.
Motivated by these observations, I present my recent research on low-angular-momentum accretion flows onto supermassive black holes within both the Newtonian and general-relativistic frameworks, using semi-analytical models and general-relativistic hydrodynamic (GRHD) simulations.
The study covers a wide range of spatial scales, extending from the event horizon to the Bondi radius (approximately (10^{5.7}) Schwarzschild radii).
Within the semi-analytical framework, I investigate the effects of outflows, outer boundary conditions, and the gravitational potential of the host galaxy, including both the stellar component and the dark matter halo, on the structure and dynamics of the accretion flow.
I also present GRHD simulations of quasi-spherical accretion onto a black hole embedded in a dark matter halo. These simulations explore how modifications to the spacetime geometry induced by the surrounding dark matter influence the properties and dynamics of the accretion flow. Finally, I will present a summary of my current research and discuss future directions.
