Tracing the Outflow of a z=0.334 FeLoBAL: New Constraints from
  Low-Ionization Absorbers in FBQS J1151+3822
  We show for the first time that FBQS J1151+3822 is an iron low-ionization
broad absorption line quasar (FeLoBAL QSO), the second-brightest and
second-closest known example of this class. He I* and Fe II together act as an
effective analytical tool, allowing us to obtain useful kinematic constraints
from photoionization models of the outflow without needing to assume any
particular acceleration model. The main outflow's log ionization parameter is
-1.5, the log hydrogen density [cm^(-3)] 5.5 to 8, the log hydrogen column
density [cm^(-2)] 21.7 to 21.9, the absorption radius 7.2 to 127 pc, and the
kinetic luminosity 0.16% to 4.5% of the bolometric luminosity. We obtain
line-of-sight covering fractions of ~0.25 for strong Fe II, ~0.5 for He I*, and
~0.6 for Mg II. Narrower and shallower absorption lines from weaker Fe II and
Mn II with outflow velocity ~3400 km/s have appeared between 2005 and 2011,
suggesting that dense cores may have condensed inside the main outflow.
Consideration of the literature might suggest that the FBQS J1151+3822 outflow
is a member of a rare and distinct sub-class of FeLoBALs with high densities
and correspondingly small absorption radii. We find, however, that such
outflows are not necessarily a distinct sub-class, and that their apparent
rarity could be a symptom of selection bias in studies using density-sensitive
lines.
