Pushpa Khare,¹ V. P. Kulkarni,² J. T. Lauroesch,³ S. M. Fall,⁴ D. G. York,⁵ D. E. Welty,⁵ A.P.S. Crotts,⁶ J. W. Truran,⁵ and O. Nakamura^7
1Physics Department, Utkal University, Bhubaneswar, 751004, India
²Department of Physics and Astronomy, University of South Carolina, Columbia, SC 29208,USA
³Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA
⁴Space Telescope Science Institute, Baltimore, MD 21218, USA
⁵Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA
⁶Department of Astronomy, Columbia University, New York, NY 10027, USA
⁷School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK

Abstract. With the aim of determining the evolution of metals and dust in the universe, we have observed 8 Damped Lyman-alpha Absorbers (DLAs) with the Multiple Mirror Telescope and the Hubble Space Telescope at 0:1 < z < 1:5, including several absorbers discovered in the Sloan Digital Sky Survey. These measurements have more than doubled the sample of Zn and Cr measurements at z < 1:5 and added three measurements at z < 0:4, where none existed before. In contradiction with the predictions of most chemical evolution models, our data suggest that the global mean metallicity of DLAs, as measured by the gas phase abundance of Zn, at best evolves weakly with redshift over the range 0:09 < z < 3:9 and does not seem to rise to the solar level even at very low redshifts. The dust content, as determined by [Cr/Zn], does not show much change with redshift.

Keywords: cosmology: observations - galaxies: abundances - galaxies: evolution - quasars: absorption lines

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