Metal enrichment by radiation pressure in active galactic nucleus
  outflows -- theory and observations
  Outflows from active galactic nuclei may be produced by absorption of
continuum radiation by UV resonance lines of abundant metal ions, as observed
in broad absorption line quasars (BALQs). The radiation pressure exerted on the
metal ions is coupled to the rest of the gas through Coulomb collisions of the
metal ions. We calculate the photon density and gas density which allow
decoupling of the metal ions from the rest of the gas. These conditions may
lead to an outflow composed mostly of the metal ions. We derive a method to
constrain the metals/H ratio of observed UV outflows, based on the Ly {\alpha}
and Si iv {\lambda}{\lambda}1394, 1403 absorption profiles. We apply this
method to an SDSS sample of BALQs to derive a handful of candidate outflows
with a higher than solar metal/H ratio. This mechanism can produce ultra fast
UV outflows, if a shield of the continuum source with a strong absorption edge
is present.
