The Physics and Physical Properties of Quasar Outflows
  We describe two studies designed to characterize the total column densities,
kinetic energies, and acceleration physics of broad absorption line (BAL)
outflows in quasars. The first study uses new Chandra X-ray and ground-based
rest-frame UV observations of 7 quasars with mini-BALs at extreme high speeds,
in the range 0.1c to 0.2c, to test the idea that strong radiative shielding is
needed to moderate the mini-BAL ionizations and facilitate their acceleration
to extreme speeds. We find that the X-ray absorption is weak or absent, with
generally N_H < few x 10^22 mc^-2, and that radiative shielding is not
important. We argue that the mini-BAL ionizations are controlled, instead, by
high gas densities of order n_H ~ 4 x 10^8 cm^-3 in small outflow
substructures. If we conservatively assume that the total column density in the
mini-BAL gas is N_H < 10^22 cm^-2, covering >15% of the UV continuum source
along our lines of sight (based on measured line depths), then the radial
thickness of these outflows is only Delta_R < 3 x 10^13 cm and their transverse
size is > 8 x 10^15 cm. Thus the outflow regions have the shape of very thin
"pancakes" viewed face-on, or they occupy larger volumes like a spray of dense
cloudlets with a very small volume filling factor. We speculate that this
situation (with ineffective shielding and small dense outflow substructures)
applies to most quasar outflows, including BALs. Our second study focuses from
BALs of low-abundance ions, mainly PV 1118,1128 A, whose significant strengths
imply large column densities, N_H > 10^22 cm^-2, that can further challenge
models of the outflow acceleration. In spite of the difficulties of finding
this line in the Ly-alpha forest, a search through the SDSS DR9 quasar catalog
reveals >50 BAL sources at redshifts z>2.3 with strong PV BALs, which we are
now using to characterize the general properties of high-column outflows.
