Elemental abundances in two high column density damped Lyα systems at z < 1.5

We present Keck HIRES abundance measurements and metal-line kinematic profiles of the damped Lyalpha systems (DLAs) toward the quasars Q0933+733 (z(abs) = 1.479) and Q0948+433 (z(abs) = 1.233). These two DLAs have among the five highest H I column densities at any redshift: N(H I) = 4.2 x 10(21) cm(-2). The metal-line data, presented here for the first time, reveal that these DLAs are noteworthy for several other reasons as well. ( 1) The Q0933+733 DLA exhibits a simple kinematic structure with unusually narrow velocity widths as measured from its unsaturated metal lines (Deltav = 16 km s(-1)). At 2.6% solar, it has the second lowest metallicity at z < 2. (2) The Q0948+433 DLA has among the strongest metal-line transitions of any known DLA. The saturated Si II lambda 1808 line implies a high metallicity ([Si/H] > -1) and a significant alpha-enhancement. The strong metal lines of this DLA have made possible the detection of Ti II lambda1910, Co II lambda2012, and Mg I lambda2026. (3) We find that the relative gas-phase abundances of both DLAs follow the general trend seen at high redshift, e.g., enhanced Zn/Fe and Si/Fe and subsolar Mn/Fe, indicating that there is little evolution in the nucleosynthetic patterns of DLAs down to this epoch. (4) Their high H I column densities imply that these DLAs dominate the column density-weighted cosmic mean metallicity, [Z], of the universe at z < 1.5. Using the 15 DLAs with measured metallicities in the redshift interval 0.4 < z < 1.5, we find [Z] = - 0.89(-0.33)(+0.40) where the uncertainties are 95% confidence limits.