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Galactic Chemical Abundances at z>3 I: First Results from the Echellette Spectrograph and Imager

Jason X. Prochaska·Eric Gawiser·Arthur M. Wolfe
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Abstract

We present the first results from an ongoing survey to discover and measure the metallicity of z>3 damped Lya systems with the Echellette Spectrograph and Imager (ESI) on the Keck II telescope. Our motivation arises from a recent study on the damped Lya systems suggesting only mild evolution in the cosmic metallicity from z~2 to 4. The Echellette Spectrograph and Imager, which provides two complementary spectroscopic modes, is the ideal instrument for a z>3 damped Lya survey. We describe our observing strategy and report on the discovery and analysis of 5 new z>3 damped Lya systems acquired in a single night of observing. These observations further support the principal conclusions of the previous study: (1) the cosmic metallicity in neutral gas inferred from the damped Lya systems does not evolve significantly from z~2 to 4; (2) the unweighted metallicity exhibits a statistically significant decrease with increasing redshift; and (3) not a single damped Lya system has a metallicity below [Fe/H]=-3. We discuss the implications of these results and comment on recent theoretical studies which attempt to explain the observations.

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Jason X. Prochaska, Eric Gawiser, Arthur M. Wolfe. 2001-01-03. Galactic Chemical Abundances at z>3 I: First Results from the Echellette Spectrograph and Imager. https://doi.org/10.1086/320467

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