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[38.06] Abundances in Star-forming Galaxies and Damped Lyman Alpha Systems

R. Schulte-Ladbeck, S. M. Rao, A. M. Hopkins, B. König, D. A. Turnshek (UPitt), C. J. Miller (CTIO), D. Vanden Berk (Penn State)

Our knowledge about the chemical properties of galaxies is based on measurements of emission lines from photo-ionized gas. The abundances of galaxies at high-z are inferred using absorption lines arising in neutral gas in Damped Lyman Alpha (DLA) systems. Do the results of emission and absorption experiments agree in cases of nearby star-forming galaxies (SFGs) causing DLAs?

Schulte-Ladbeck et al. (2004a) examined the z=0.009 DLA/SFG SBS~1543+593. We derived [O/H]_II=-0.54. The bright QSO HS~1543+5921 intercepts the disk at small impact parameter. We found a lower limit, [O/H]_I>-2.14, using HST archival spectra. New HST observations by Bowen et al. are analyzed to yield a S abundance of [S/H]_I=-0.54. Using S as a proxy for O this suggests [O/H]_I=[O/H]_II (or 0.29xsolar) for one genuine DLA.

To investigate additional SFG/QSO pairs, we used the CMU-Pitt Value Added Catalog to assemble from the SDSS DR1 a database of about 13,000 SFGs with 0< z <0.36 (Schulte-Ladbeck 2004b). We applied the strong-line indices of Pettini & Pagel (2004), derived O/H_II for all objects, and a median O/H_II ratio of 0.74xsolar with a SIQR of 0.19. An O/H vs. z diagram is constructed by augmenting these data to z\approx5 with O/H_I ratios for DLAs (Prochaska et al. 2003). We matched our SFG catalog against the SDSS QSO catalog, then used the HST archive to determine the HI column densities and limits on O/H_I for these SFGs. The results are discussed using the O/H vs. redshift diagram.

We acknowledge support of HST archival funding to program ID 10282.

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.