A Variable PV Broad Absorption Line and Quasar Outflow Energetics
  Broad absorption lines (BALs) in quasar spectra identify high velocity
outflows that might exist in all quasars and could play a major role in
feedback to galaxy evolution. The viability of BAL outflows as a feedback
mechanism depends on their kinetic energies, as derived from the outflow
velocities, column densities, and distances from the central quasar. We
estimate these quantities for the quasar, Q1413+1143 (redshift $z_e = 2.56$),
aided by the first detection of PV $\lambda\lambda$1118,1128 BAL variability in
a quasar. In particular, PV absorption at velocities where the CIV trough does
not reach zero intensity implies that the CIV BAL is saturated and the absorber
only partially covers the background continuum source (with characteristic size
<0.01 pc). With the assumption of solar abundances, we estimate that the total
column density in the BAL outflow is log N_H > 22.3 (cm^-2). Variability in the
PV and saturated CIV BALs strongly disfavors changes in the ionization as the
cause of the BAL variability, but supports models with high-column density BAL
clouds moving across our lines of sight. The observed variability time of 1.6
yr in the quasar rest frame indicates crossing speeds >750 km/s and a radial
distance from the central black hole of <3.5 pc, if the crossing speeds are
Keplerian. The total outflow mass is ~4100 M_solar, the kinetic energy ~4x10^54
erg, and the ratio of the outflow kinetic energy luminosity to the quasar
bolometric luminosity is ~0.02 (at the minimum column density and maximum
distance), which might be sufficient for important feedback to the quasar's
host galaxy.
