Quasars Probing Quasars VIII. The Physical Properties of the Cool
  Circumgalactic Medium Surrounding z ~ 2-3 Massive Galaxies Hosting Quasars
  We characterize the physical properties of the cool T ~10^4 K circumgalactic
medium surrounding z ~2-3 quasar host galaxies, which are predicted to evolve
into present day massive ellipticals. Using a statistical sample of 14 quasar
pairs with projected separation < 300 kpc and high dispersion, high S/N
spectra, we find extreme kinematics with low metal ion lines typically spanning
~ 500 km/s, exceeding any previously studied galactic population. The CGM is
significantly enriched, even beyond the virial radius, with a median
metallicity [M/H] ~ -0.6. The alpha/Fe abundance ratio is enhanced, suggesting
that halo gas is primarily enriched by core-collapse supernovae. The projected
cool gas mass within the virial radius is estimated to be 1.9*10^11 M_sun
(R_\perp/160 kpc)^2, accounting for ~ 1/3 of the galaxy halo baryonic budget.
The ionization state of CGM gas increases with projected distance from the
foreground quasars, contrary to expectation if the quasar dominates the
ionizing radiation flux. However, we also found peculiarities not exhibited in
the CGM of other galaxy populations. In one absorption system, we may be
detecting unresolved fluorescent Ly-alpha emission, and another system shows
strong NV lines. Taken together these anomalies suggest that transverse
sightlines are at least in some cases possibly illuminated. We also discovered
a peculiar case where detection of the CII* fine structure line implies an
electron density > 100 cm^-3 and subparsec scale gas clumps.
