Assessing the dust selection bias in quasar absorbers at 0.7 < z< 1.6: Zn/Fe abundances in a radio-selected sample

TL;DR

This study investigates dust bias in quasar absorber surveys at intermediate redshifts by analyzing metal abundances in a radio-selected sample, finding no significant dust bias affecting DLA statistics.

Contribution

It provides new measurements of metal abundances and dust-to-metals ratios in MgII absorbers at 0.7<z<1.6, assessing dust bias in optical surveys using a radio-selected sample.

Findings

Dust-to-metals ratios are consistent with optical samples.

Number density of DLAs aligns with optical survey results.

Discovered 4 new absorbers, including confirmed DLAs.

Abstract

The Complete Optical and Radio Absorption Line System (CORALS) survey has previously been used to demonstrate that the number density, gas and metals content of z>1.6 damped Lyman alpha systems is not significantly under-estimated in magnitude limited surveys. In this paper, a sample of strong MgII absorbers selected from the optically complete 0.7 < z < 1.6 CORALS sample of Ellison et al. is used to assess the potential of dust bias at intermediate redshifts. From echelle spectra of all CORALS absorbers with MgII lambda 2796 and FeII lambda 2600 rest equivalent widths > 0.5 A in the redshift range 0.7 < z < 1.6, we determine column densities of Zn, Cr, Fe, Mn and Si. The range of dust-to-metals ratios and inferred number density of DLAs from the D-index are consistent with optical samples. We also report the discovery of 4 new absorbers in the echelle data in the redshift range 1.7 < z< 2.0, two of which are confirmed DLAs and one is a sub-DLA, whilst the Lya line is not covered for the fourth.