Elemental abundance measurements in low-redshift damped Lyman α absorbers

We present elemental abundance measurements for nine damped Lyman alpha (Ly alpha) systems (DLAs) and one sub-DLA at 0.1 less than or similar to z less than or similar to 1.5 from recent observations with the Multiple Mirror Telescope (MMT). Most of these absorbers are found to be metal poor, while two are found to have approximate to 30-50 per cent solar metallicities. Combining our data with other data from the literature, we find that the systems with higher [Zn/H] also have stronger depletion as measured by [Cr/Zn] and [Fe/Zn]. The relationship between the metallicity and H I column density is also investigated. Together with our previous MMT survey, we have discovered two of the four known absorbers at z < 1.5 that lie above (although near) the 'obscuration threshold'. This appears to be a result of selecting absorbers with strong metal lines in our sample. It would be interesting to find other similar systems by observing a larger sample and study how much such systems contribute to the cosmic budget of metals. Finally, an analysis of the N-H I-weighted mean metallicity versus redshift for our sample combined with data from the literature supports previous conclusions that the N-H I-weighted mean global DLA metallicity rises slowly at best and falls short of solar levels by a factor of > 4 even at z = 0.