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The evolution of damped Ly-$\alpha$ absorbers: metallicities and star formation rates

Published online by Cambridge University Press:  06 October 2005

Varsha P. Kulkarni
Affiliation:
Dept. of Physics and Astronomy, Univ. of South Carolina, Columbia, SC 29208, USA emails: kulkarni@sc.edu; meiring@physics.sc.edu; thatte@physics.sc.edu
Donald G. York
Affiliation:
Dept. of Astronomy and Astrophysics, Univ. of Chicago, Chicago, IL 60637, U.S.A. email: don@oddjob.uchicago.edu
James T. Lauroesch
Affiliation:
Dept. of Physics and Astronomy, Northwestern Univ., Evanston, IL 60208, USA email: jtl@elvis.astro.northwestern.edu
S. Michael Fall
Affiliation:
Space Telescope Science Inst., Baltimore, MD 21218, U.S.A. email: fall@stsci.edu
Pushpa Khare
Affiliation:
Dept. of Physics, Utkal University, Bhubaneswar, 751004, India email: khare@iopb.res.in
Bruce E. Woodgate
Affiliation:
NASA/Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, U.S.A. email: woodgate@uit.gsfc.nasa.gov
Povilas Palunas
Affiliation:
McDonald Observatory, Univ. of Texas, Austin, TX 78712, U.S.A. email: palunas@astro.as.utexas.edu
Joseph Meiring
Affiliation:
Dept. of Physics and Astronomy, Univ. of South Carolina, Columbia, SC 29208, USA emails: kulkarni@sc.edu; meiring@physics.sc.edu; thatte@physics.sc.edu
Deepashri G. Thatte
Affiliation:
Dept. of Physics and Astronomy, Univ. of South Carolina, Columbia, SC 29208, USA emails: kulkarni@sc.edu; meiring@physics.sc.edu; thatte@physics.sc.edu
Daniel E. Welty
Affiliation:
Dept. of Astronomy and Astrophysics, Univ. of Chicago, Chicago, IL 60637, U.S.A. email: don@oddjob.uchicago.edu
James W. Truran
Affiliation:
Dept. of Astronomy and Astrophysics, Univ. of Chicago, Chicago, IL 60637, U.S.A. email: don@oddjob.uchicago.edu
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Abstract

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Damped Lyman-$\alpha$ (DLA) and sub-DLA quasar absorption lines provide powerful probes of the evolution of metals, gas, and stars in galaxies. One major obstacle in trying to understand the evolution of DLAs and sub-DLAs has been the small number of metallicity measurements at $z<1.5$, an epoch spanning $\sim 70$% of the cosmic history. In recent surveys with the Hubble Space Telescope and Multiple Mirror Telescope, we have doubled the DLA Zn sample at $z<1.5$. Combining our results with those at higher redshifts from the literature, we find that the global mean metallicity of DLAs does not rise to the Solar value at low redshifts. These surprising results appear to contradict the near-Solar mean metallicity observed for nearby ($z \approx 0$) galaxies and the predictions of cosmic chemical evolution models based on the global star formation history. Finally, we discuss direct constraints on the star formation rates (SFRs) in the absorber galaxies from our deep Fabry-Perot Ly-$\alpha$ imaging study and other emission-line studies in the literature. A large fraction of the observed heavy-element quasar absorbers at $0<z<3.4$ appear to have SFRs substantially below the global mean SFR, consistent with the low metallicities observed in the spectroscopic studies.

Type
Contributed Papers
Copyright
© 2005 International Astronomical Union