Density profile of ambient circumnuclear medium in Seyfert 1 galaxies

TL;DR

This study introduces a new method to measure the density profile of the ambient circumnuclear medium in Seyfert 1 galaxies by analyzing the equilibrium between radiation pressure and drag pressure on warm absorbers, revealing a steeper profile than some models predict.

Contribution

The paper presents a novel approach to determine the ACM density profile in AGNs using outflow properties, providing new insights into the circumnuclear environment of Seyfert 1 galaxies.

Findings

ACM density profile ranges between n∝ r^-1.7 and r^-2.15

Profile is steeper than Bondi accretion and hot flow models

Profile aligns more with standard thin disk predictions

Abstract

The shape of the ambient circumnuclear medium (ACM) density profile can probe the history of accretion onto the central supermassive black hole in galaxies and the circumnuclear environment. However, due to the limitation of the instrument resolution, the density profiles of the ACM for most of galaxies remain largely unknown. In this work, we propose a novel method to measure the ACM density profile of active galactic nucleus (AGN) by the equilibrium between the radiation pressure on the warm absorbers (WAs, a type of AGN outflows) and the drag pressure from the ACM. We study the correlation between the outflow velocity and ionization parameter of WAs in each of the five Seyfert 1 galaxies (NGC 3227, NGC 3783, NGC 4051, NGC 4593, and NGC 5548), inferring that the density profile of the ACM is between n\propto r^-1.7 and n \propto r^-2.15 (n is number density and r is distance) from 0.01 pc to pc scales in these five AGNs. Our results indicate that the ACM density profile in Seyfert 1 galaxies is steeper than the prediction by the spherically symmetric Bondi accretion model and the simulated results of the hot accretion flow, but more in line with the prediction by the standard thin disk model.