Quasars Probing Quasars VII. The Pinnacle of the Cool Circumgalactic
  Medium Surrounds Massive z~2 Galaxies
  We survey the incidence and absorption strength of the metal-line transitions
CII 1334 and CIV from the circumgalactic medium (CGM) surrounding z~2 quasars,
which act as signposts for massive dark matter halos M_halo~10^12.5 Msun. On
scales of the virial radius (Mvir~160kpc), we measure a high covering fraction
fC=0.73+/-0.10 to strong CII absorption (rest equivalent width W1334>0.2A),
implying a massive reservoir of cool (T~10^4K) metal enriched gas. We
conservatively estimate a metal mass exceeding 10^8 Msun. We propose these
metals trace enrichment of the incipient intragroup/intracluster medium that
these halos eventually inhabit. This cool CGM around quasars is the pinnacle
amongst galaxies observed at all epochs, as regards covering fraction and
average equivalent width of HI Lya and low-ion metal absorption. We argue that
the properties of this cool CGM primarily reflect the halo mass, and that other
factors such as feedback, star-formation rate, and accretion from the
intergalactic medium are secondary. We further estimate, that the CGM of
massive, z~2 galaxies accounts for the majority of strong MgII absorption along
random quasar sightlines. Lastly, we detect an excess of strong CIV absorption
(W1548>0.3A) over random incidence to 1Mpc physical impact parameter and
measure the quasar-CIV cross-correlation function: xi(r)=(r/r0)^-g with r0 =
7.5Mpc and g=1.7. Consistent with previous work on larger scales, we infer that
this highly ionized CIV gas traces massive (10^12 Msun) halos.
