Mass Loss by X-ray Winds from Active Galactic Nuclei

TL;DR

This study analyzes high-quality X-ray spectra of type-I AGN to characterize ionized winds, estimate their mass loss rates, and understand their physical properties and implications for AGN feedback.

Contribution

Introduces a novel modeling scheme for gaseous winds in AGN, revealing their multi-phase nature, thermal driving origin, and comparable mass loss to accretion rates.

Findings

Outflows are multi-phase with similar kinematics.

Winds are thermally driven from parsec scales.

Mass loss rates are comparable to accretion rates.

Abstract

We consider a sample of type-I active galactic nuclei (AGN) that were observed by Chandra/HETG and resulted in high signal-to-noise grating spectra, which we study in detail. All objects show signatures for very high ionization outflows. Using a novel scheme to model the physics and spectral signatures of gaseous winds from these objects, we are able to estimate the mass loss rates and kinetic luminosities associated with the highly ionized gas and investigate its physical properties. Our conclusions are as follows: 1) There is a strong indication that the outflowing gas in those objects is multi-phase with similar kinematics for the different phases. 2) The X-ray spectrum is consistent with such flows being thermally driven from ~pc scales, and are therefore unlikely to be associated with the inner accretion disk. 3) The underlying X-ray spectrum consists of a hard X-ray powerlaw which is similar for all objects shining below their Eddington rate and a soft excess whose contribution becomes more prominent for objects shining close to their Eddington limit. 4) The physical properties of the outflow are similar in all cases and a coherent picture emerges concerning its physical properties. 5) The deduced mass loss rates are, roughly, of the order of the mass accretion rate in those objects so that the kinetic luminosity carried by such winds is only a tiny fraction (<<1%) of the bolometric luminosity. We discuss the implications of our results for AGN structure and AGN interaction with the environment.