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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We present the first results from an ongoing survey to discover and measure the metallicity of z > 3 damped Lyα systems with the Echellette Spectrograph and Imager (ESI) on the Keck II telescope. Our motivation arises from a recent study on damped Lyα 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 Lyα survey. We describe our observing strategy and report on the discovery and analysis of five new z > 3 damped Lyα 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 Lyα 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 Lyα system has a metallicity below [Fe/ H] = -3. We discuss the implications of these results and comment on recent theoretical studies that attempt to explain the observations.

Original languageEnglish (US)
Pages (from-to)99-105
Number of pages7
JournalAstrophysical Journal
Issue number1 PART 1
StatePublished - May 1 2001

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Galaxies: ISM
  • Galaxies: abundances
  • Intergalactic medium
  • Quasars: absorption lines


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