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J.X. Prochaska (Carnegie Observatories), A.M. Wolfe, E.J. Gawiser (UC San Diego)
In a previous paper we demonstrated that the mean metallicity of damped Ly\alpha systems exhibits no significant evolution from z=2-4. This result is surprising because it contradicts nearly every model of chemical evolution in the early universe. At z>3, however, the analysis was based on only ~10 systems and suffered from small number statistics. To address this concern we have initiated a survey of z>3 damped Ly\alpha systems with the new Echellette Spectrograph and Imager (ESI) on the Keck~II telescope. By taking advantage of the unique capabilities of ESI, we are efficiently discovering and measuring the metallicity of many new z>3 damped systems. This paper presents the first results of the survey including [Fe/H] measurements of more than 10 new systems. The combined sample still indicates minimal evolution in the mean metallicity from z=2-4 but at higher statistical significance. In the next few years we expect to identify N ~40 new systems and robustly examine the chemical enrichment history of galaxies in the early universe.
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