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 (DLA) systems is not significantly underestimated in magnitude limited surveys. In this paper, a sample of strong Mg ii 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 Mg ii ?2796 and Fe ii ?2600 rest equivalent widths >0.5 Å 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 four 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. © 2009 RAS.