The location and kinematics of the coronal-line emitting regions in AGN

TL;DR

This paper models the location and movement of high-ionisation emission gas in an active galaxy, revealing it originates near the dusty torus and is driven outward by radiation, balancing gravity and outflows.

Contribution

It provides a physical model explaining the origin, acceleration, and kinematics of FHIL emitting gas in AGN, linking it to the dusty torus and galaxy interactions.

Findings

FHIL gas is launched from the dusty torus.

Gas reaches terminal velocity of a few hundred km/s.

Outflow is influenced by radiative forces and gravitational interactions.

Abstract

We use the photoionisation code Cloudy to determine both the location and the kinematics of the optical forbidden, high ionisation line (hereafter, FHIL) emitting gas in the narrow line Seyfert 1 galaxy Ark 564. The results of our models are compared with the observed properties of these emission lines to produce a physical model that is used to explain both the kinematics and the source of this gas. The main features of this model are that the FHIL emitting gas is launched from the putative dusty torus and is quickly accelerated to its terminal velocity of a few hundred km/s. Iron-carrying grains are destroyed during this initial acceleration. This velocity is maintained by a balance between radiative forces and gravity in this super-Eddington source. Eventually the outflow is slowed at large radii by the gravitational forces of and interactions with the host galaxy. In this model, FHIL emission traces the transition between the AGN and bulge zones of influence.