Dust, Metals and Diffuse Interstellar Bands in Damped Lyman Alpha Systems

Abstract

Although damped Lyman alpha (DLA) systems are usually considered metal-poor, it has been suggested that this could be due to observational bias against metal-enriched absorbers. I review recent surveys to quantify the particular issue of dust obscuration bias and demonstrate that there is currently no compelling observational evidence to support a widespread effect due to extinction. On the other hand, a small sub-set of DLAs may be metal-rich and I review some recent observations of these metal-rich absorbers and the detection of diffuse interstellar bands in one DLA at z ~ 0.5.