Damped Systems Associated with a Galaxy Cluster at Z=2.38

Abstract

We have found a unique cluster of three damped Lyman-alpha systems at redshift 2.38 seen in absorption against three background QSOs. One of the damped systems lies in the centre of a rich galaxy cluster - indeed it lies less than 150 kpc from a pair of giant elliptical galaxies. Despite this dense environment the gas is cold and has a metallicity of only -2.7 dex. Another damped system lies roughly 10 co-moving Mpc away in the middle of a void. Despite this low density location it has a much higher metallicity: around -1.5 dex.

We conclude that there is no strong correlation between the environments of damped systems and their metallicities at thigh redshifts. Damped systems in the middle of clusters can hav very low metallicities while damped systems in voids can be substantially enriched.