Accretion environments of active galactic nuclei

TL;DR

This paper models the complex accretion and excretion flows around supermassive black holes in active galactic nuclei, highlighting the formation of rings, disks, and winds influenced by black hole motion and angular momentum transfer.

Contribution

It introduces a detailed theoretical framework for accretion and excretion structures around wandering supermassive black holes, incorporating recent findings on ring composition and flow dynamics.

Findings

Formation of a thick envelope and thin core in the accretion ring.

Prediction of a super-sonic wind from the excretion flow.

Collimation of flows into bipolar cones by interactions with excretion winds.

Abstract

We study accretion environments of active galactic nuclei when a super-massive black hole wanders in a circum-nuclear region and passes through an interstellar medium there. It is expected that a Bondi-Hoyle-Lyttleton type accretion of the interstellar matter takes place and an accretion stream of matter trapped by the black hole gravitational field appears from a tail shock region. Since the trapped matter is likely to have a certain amount of specific angular momentum, the accretion stream eventually forms an accretion ring around the black hole. According to the recent study, the accretion ring consists of a thick envelope and a thin core, and angular momenta are transfered from the inner side facing to the black hole to the opposite side respectively in the envelope and the core. As a result, a thick accretion flow and a thick excretion flow extend from the envelope, and a thin accretion disk and a thin excretion disk do from the core. The thin excretion disk is predicted to terminate at some distance forming an excretion ring, while the thick excretion flow is considered to become a super-sonic wind flowing to the infinity. The thick excretion flow from the accretion ring is expected to interact with the accretion stream toward the accretion ring and to be collimated to bi-polar cones. These pictures provide a likely guide line to interpret the overall accretion environments suggested from observations.