Criterions for retrograde rotation of accreting black holes

TL;DR

This paper investigates the characteristics of retrograde accreting black holes in active galactic nuclei, identifying low Eddington ratio AGNs as prime candidates for retrograde systems, which has implications for black hole mergers.

Contribution

It provides criteria for identifying retrograde accreting black holes in observed AGNs, highlighting low Eddington ratio systems as the best candidates.

Findings

AGNs with low Eddington ratios are prime retrograde candidates

Retrograde systems are prevalent among kinetically dominated FRII radio galaxies and narrow line Seyfert I galaxies

Retrograde accretion enhances black hole binary merger efficiency

Abstract

Rotating supermassive black holes produce jets and their origin is connected to magnetic field that is generated by accreting matter flow. There is a point of view that electromagnetic fields around rotating black holes are brought to the hole by accretion. In this situation the prograde accreting disks produce weaker large-scale black hole threading magnetic fields, implying weaker jets that in retrograde regimes. The basic goal of this paper is to find the best candidates for retrograde accreting systems in observed active galactic nuclei. We show that active galactic nuclei with low Eddington ratio are really the best candidates for retrograde systems. This conclusion is obtained for kinetically dominated FRII radio galaxies, flat spectrum radio loud narrow line Seyfert I galaxies and a number of nearby galaxies. Our conclusion is that the best candidates for retrograde systems are the noticeable population of active galactic nuclei in the Universe. This result corresponds to the conclusion that in the merging process the interaction of merging black holes with a retrograde circumbinary disk is considerably more effective for shrinking the binary system.