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

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.

Accepted for publication in MNRAS

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• Using 21cm Absorption in Small Impact Parameter Galaxy-QSO Pairs to Probe Low-Redshift Damped and Sub-Damped Lyman-alpha System
• The ESO UVES Advanced Data Products Quasar Sample - III. Evidence of Bimodality in the [N/alpha] Distribution
• FLASH Early Science -- Discovery of an intervening HI 21-cm absorber from an ASKAP survey of the GAMA 23 field
• MusE GAs FLOw and Wind (MEGAFLOW) V. The dust/metallicity-anisotropy of the Circum-Galactic Medium
• Casting light on the 'anomalous' statistics of Mg II absorbers toward Gamma-Ray Burst afterglows: the incidence of weak systems
• A quasar hiding behind two dusty absorbers. Quantifying the selection bias of metal-rich, damped Lyman-alpha absorption systems
• The ESO UVES Advanced Data Products Quasar Sample - IV. On the deficiency of Argon in DLA systems