Unusual Metal Abundances in a Pair of Damped Lyman Alpha Systems at z~2

Abstract

We present high resolution spectroscopic observations of two neighbouring damped Lya systems (DLAs) along the same line of sight towards B2314-409. Due to their separation (v ~ 2000 km/s) and the high spectral resolution of the data, it is possible to fit not only the weak metal transitions, but also the separate HI absorption profiles. This has permitted, for the first time, a detailed study of metal abundances in two neighbouring galaxy-scale absorbers. The two DLAs have z_abs = 1.8573 and 1.8745 and have column densities log N(HI) = 20.9+/-0.1 and 20.1+/-0.2 respectively. We have determined abundances for a range of chemical elements, and find that BOTH absorbers towards B2314-409 have low alpha/Fe-peak abundances compared with other known DLAs. This indicates that not only has the recent star formation history of these absorbers been relatively passive, but that the group environment, or some other external factor, may have influenced this.

Accepted for publication in A&A, erratum included

References in corpus (2)

• The CORALS Survey I: New Estimates of the Number Density and Gas Content of Damped Lyman Alpha Systems Free from Dust Bias
• Ionization Properties and Elemental Abundances in Damped Ly alpha Systems

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