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Chemical abundances of damped Lyman alpha systems in the XQ-100 survey

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(2016)cite arxiv:1609.05968Comment: Accepted to MNRAS. 19 pages plus Appendix material (102 pages total).

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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