1998ApJ...499..677C

We report the discovery of two iron-group enhanced high-metallicity Mg II absorbers in a search through 28 Lyα forest clouds along the PKS 0454+039 sight line. Based upon our survey and the measured redshift number densities of W_r(Mg II) ≤ 0.3 Å absorbers and Lyα absorbers at z ∼ 1, we suggest that roughly 5% of Lyα absorbers at z ≤ 1 will exhibit ``weak'' Mg II absorption to a 5 σ W<sub>r</sub>(λ2796) detection limit of 0.02 Å. The two discovered absorbers, at redshifts z = 0.6248 and z = 0.9315, have W<sub>r</sub>(Lyα) = 0.33 and 0.15 Å, respectively. Based upon photoionization modeling, the H I column densities are inferred to be in the range 15.8 ≤ log N(H I) ≤ 16.8 cm<sup>–2</sup>. For the z = 0.6428 absorber, if the abundance pattern is solar, then the cloud has [Fe/H] > -1; if its gas-phase abundance follows that of depleted clouds in our Galaxy, then [Fe/H] > 0 is inferred. For the z = 0.9315 absorber, the metallicity is [Fe/H] > 0, whether the abundance pattern is solar or suffers depletion. Imaging and spectroscopic studies of the PKS 0454+039 field reveal no candidate luminous objects at these redshifts. We discuss the possibility that these Mg II absorbers may arise in the class of ``giant'' low surface brightness galaxies, which have [Fe/H] ≥ -1, and even [Fe/H] ≥ 0, in their extended disks. We tentatively suggest that a substantial fraction of these ``weak'' Mg II absorbers may select low surface brightness galaxies out to z ∼ 1.