Metallicities and dust content of proximate damped Lyman alpha systems
  in the Sloan Digital Sky Survey
  Composite spectra of 85 proximate absorbers (log N(HI)>20 and velocity
difference between the absorption and emission redshift, dv<10,000 km/s) in the
SDSS are used to investigate the trends of metal line strengths with velocity
separation from the QSO. We construct composites in 3 velocity bins: dv<3000
km/s, 3000<dv<6000 km/s and dv>6000 km/s, with further sub-samples to
investigate the metal line dependence on N(HI) and QSO luminosity. Low (e.g.
SiII and FeII) and high ionization (e.g. SiIV and CIV) species alike have
equivalent widths (EWs) that are larger by factors of 1.5 -- 3 in the dv<3000
km/s composite, compared to the dv>6000 km/s spectrum. The EWs show an even
stronger dependence on dv if only the highest neutral hydrogen column density
(log N(HI)>20.7) absorbers are considered. We conclude that PDLAs generally
have higher metallicities than intervening absorbers, with the enhancement
being a function of both dv and N(HI). It is also found that absorbers near
QSOs with lower rest-frame UV luminosities have significantly stronger metal
lines. We speculate that absorbers near to high luminosity QSOs may have had
their star formation prematurely quenched. Finally, we search for the signature
of dust reddening by the PDLAs, based on an analysis of the QSO continuum
slopes relative to a control sample and determine a limit of E(B-V)<0.014 for
an SMC extinction curve. This work provides an empirical motivation for
distinguishing between proximate and intervening DLAs, and establishes a
connection between the QSO environment and galaxy properties at high redshifts.
