Metal abundances at z<1.5: new measurements in sub-Damped Lyman-alpha Absorbers

TL;DR

This study presents new measurements of metal abundances in sub-Damped Lyman-alpha absorbers at redshifts below 1.5, revealing generally high metallicities and significant abundance variations among components.

Contribution

First UVES-based measurements of metal abundances in sub-DLAs at z<1.5, expanding understanding of chemical evolution at low redshifts.

Findings

Some sub-DLAs have solar or above solar metallicity.

High metallicity observed in multiple systems, including one DLA.

Large abundance variations among different components within the same system.

Abstract

Damped Lyman-alpha systems (DLAs) and sub-DLAs seen toward background quasars provide the most detailed probes of elemental abundances. Somewhat paradoxically these measurements are more difficult at lower redshifts due to the atmospheric cut-off, and so a few years ago our group began a programme to study abundances at z < 1.5 in quasar absorbers. In this paper, we present new UVES observations of six additional quasar absorption line systems at z < 1.5, five of which are sub-DLAs. We find solar or above solar metallicity, as measured by the abundance of zinc, assumed not to be affected by dust, in two sub-DLAs: one, towards Q0138-0005 with [Zn/H]=+0.28 +/- 0.16; the other towards Q2335+1501 with [Zn/H]=+0.07 +/- 0.34. Relatively high metallicity was observed in another system: Q0123-0058 with [Zn/H]=-0.45 +/- 0.20. Only for the one DLA in our sample, in Q0449-1645, do we find a low metallicity, [Zn/H]=-0.96 +/- 0.08. We also note that in some of these systems large relative abundance variations from component to component are observed in Si, Mn, Cr and Zn.