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