Quasar Outflows and AGN Feedback in the Far UV: HST/COS Observations of QSO HE0238-1904

TL;DR

This study analyzes far UV quasar outflow spectra to determine ionization phases, outflow distance, and feedback impact, revealing a high ionization phase carrying most material and significant kinetic energy influencing galaxy evolution.

Contribution

First measurement of outflow distance using O IV/O IV* ratios in the far UV; demonstrates the outflow's role in AGN feedback with detailed ionization structure analysis.

Findings

Outflow has two ionization phases, with the high ionization phase dominating material.

Distance of the outflow from the AGN is approximately 3000 parsecs.

Mass flux is about 40 solar masses per year, with kinetic luminosity around 10^45 ergs/sec.

Abstract

Spectroscopic observations of quasar outflows at rest-frame 500-1000 Angstrom have immense diagnostic power. We present analyses of such data, where absorption troughs from three important ions are measured: first, O IV and O IV* that allow us to obtain the distance of high ionization outflows from the AGN; second, Ne VIII and Mg X that are sensitive to the very high ionization phase of the outflow. Their inferred column densities, combined with those of troughs from O VI, N IV, and H I, yield two important results: 1) The outflow shows two ionization phases, where the high ionization phase carries the bulk of the material. This is similar to the situation seen in x-ray warm absorber studies. Furthermore, the low ionization phase is inferred to have a volume filling factor of 10^(-5)-10^(-6). 2) From the O IV to O IV* column density ratio, and the knowledge of the ionization parameter, we determine a distance of 3000 pc. from the outflow to the central source. Since this is a typical high ionization outflow, we can determine robust values for the mass flux and kinetic luminosity of the outflow: 40 solar masses per year and 10^45 ergs/s, respectively, where the latter is roughly equal to 1% of the bolometric luminosity. Such a large kinetic luminosity and mass flow rate measured in a typical high ionization wind suggests that quasar outflows are a major contributor to AGN feedback mechanisms.