Quasar outflows and AGN feedback in the extreme UV: HST/COS observations of HE 0238-1904

Spectroscopic observations of quasar outflows at rest-frame 500-1000 A have immense diagnostic power. We present analyses of such data, where absorption troughs from O iv and O iv* allow us to obtain the distance of the outflows from the AGN and troughs from Ne viii and Mg x reveal the warm absorber phase of the outflow. Their inferred column densities, combined with those of 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) We determine a distance of 3000 pc from the outflow to the central source using the O iv*/O iv column density ratio and the knowledge of the ionization parameter. Since this is a typical high-ionization outflow, we can determine robust values for the outflow's mass flux and kinetic luminosity of 40 M-circle dot yr(-1) and 10(45) erg s(-1), respectively, where the latter is roughly equal to 1 per cent of the bolometric luminosity. Such a large kinetic luminosity and mass flow rate measured in a typical high-ionization wind suggest that quasar outflows are a major contributor to AGN feedback mechanisms.