Abstract
The XQ-100 survey has provided high signal-noise spectra of 100 redshift
3-4.5 quasars with the X-Shooter spectrograph. The metal abundances for 13
elements in the 41 damped Lyman alpha systems (DLAs) identified in the XQ-100
sample are presented, and an investigation into abundances of a variety of DLA
classes is conducted. The XQ-100 DLA sample contains five DLAs within 5000 km/s
of their host quasar (proximate DLAs; PDLAs) as well as three sightlines which
contain two DLAs within 10,000 km/s of each other along the same line-of-sight
(multiple DLAs; MDLAs). Combined with previous observations in the literature,
we demonstrate that PDLAs with logN(HI)<21.0 show lower S/H and Fe/H
(relative to intervening systems with similar redshift and N(HI)), whilst
higher S/H and Si/H are seen in PDLAs with logN(HI)>21.0. These abundance
discrepancies are independent of their line-of-sight velocity separation from
the host quasar, and the velocity width of the metal lines (v90). Contrary to
previous studies, MDLAs show no difference in alpha/Fe relative to single
DLAs matched in metallicity and redshift. In addition, we present follow-up
UVES data of J0034+1639, a sightline containing three DLAs, including a
metal-poor DLA with Fe/H=-2.82 (the third lowest Fe/H in DLAs identified to
date) at z=4.25. Lastly we study the dust-corrected Zn/Fe, emphasizing that
near-IR coverage of X-Shooter provides unprecedented access to MgII, CaII and
TiII lines (at redshifts 3-4) to provide additional evidence for subsolar
Zn/Fe ratio in DLAs.
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