Toroidal magnetic fields in self-gravitating disks around black holes

TL;DR

This paper models magnetized, self-gravitating disks around black holes, exploring how toroidal magnetic fields affect their structure and solution bifurcations, revealing two distinct solution branches related to disk mass.

Contribution

It introduces new models of magnetized, self-gravitating disks with different magnetic field prescriptions, analyzing their bifurcation structure and the influence of magnetic fields.

Findings

Existence of two solution branches: light and massive disks.

Magnetic fields influence the bifurcation and stability of disk solutions.

Geometric properties of spacetime explain the massive disk branch.

Abstract

We investigate stationary models of magnetized, self-gravitating disks around black holes. The disks are assumed to rotate according to a recently introduced Keplerian rotation law. We consider different prescriptions of the toroidal magnetic field. Similarly to the purely hydrodynamical case (i.e., with no magnetic field), we observe a bifurcation in the parameter space of solutions. There are usually two branches of solutions: a branch corresponding to relatively light disks and a branch for which the disk can be more massive than the black hole. The existence of this latter branch can be explained by geometric properties of the spacetime. We investigate the influence of the magnetic field in the disk on these effects.