2015ApJ...815...24K

We report Keck/Echellette Spectrograph and Imager and Very Large Telescope/Ultraviolet-Visual Echelle Spectrograph observations of three super-damped Lyα quasar absorbers with H i column densities log N_ H i_{#8805} 21.7 at redshifts 2 ≲ z ≲ 2.5. All three absorbers show similar metallicities (~-1.3 to -1.5 dex), and dust depletion of Fe, Ni, and Mn. Two of the absorbers show supersolar [S/Zn] and [Si/Zn]. We combine our results with those for other damped Lyα a absorbers (DLAs) to examine trends between N_H i_, metallicity, and dust depletion. A larger fraction of the super-DLAs lie close to or above the line [X/H] = 20.59 - log N_H i_in the metallicity versus N_H i_plot, compared to the less gas-rich DLAs, suggesting that super-DLAs are more likely to be rich in molecules. Unfortunately, our data for Q0230-0334 and Q0743+1421 do not cover H₂absorption lines. For Q1418+0718, some H₂lines are covered, but not detected. CO is not detected in any of our absorbers. For DLAs with log N_ H i_< 21.7, we confirm strong correlation between metallicity and Fe depletion, and find a correlation between metallicity and Si depletion. For super-DLAs, these correlations are weaker or absent. The absorbers toward Q0230-0334 and Q1418+0718 show potential detections of weak Lyα emission, implying star formation rates of ∼1.6 and ∼0.7 M_☉/yr, respectively (ignoring dust extinction). Upper limits on the electron densities from C ii*/C ii or Si ii*/Si ii are low, but are higher than the median values in less gas-rich DLAs. Finally, systems with log N_H i_> 21.7 may have somewhat narrower velocity dispersions Δv₉₀than the less gas-rich DLAs, and may arise in cooler and/or less turbulent gas.