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

TL;DR

This study analyzes the chemical abundances in 41 damped Lyman alpha systems from the XQ-100 survey, revealing differences based on proximity to quasars and presenting new low-metallicity DLA data, with implications for understanding galaxy evolution.

Contribution

It provides the first comprehensive analysis of metal abundances in the XQ-100 DLA sample, including new insights into proximity effects and low-metallicity systems, using high-quality spectra.

Findings

PDLAs with lower N(HI) show reduced [S/H] and [Fe/H]

Higher [S/H] and [Si/H] observed in PDLAs with N(HI)>21.0

MDLAs show no difference in [alpha/Fe] compared to single DLAs

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.