2005MNRAS.357..354E

We have obtained optical spectra of four galaxies associated with Mgii quasi-stellar object (QSO) absorbers at redshifts 0.10 < z < 0.45. We calculate the gas-phase oxygen abundance of these galaxies using the empirical R₂₃strong-line method. The absolute B-band magnitudes of the galaxies span -20.6 < M_B < -18.3. If the metallicities lie on the R₂₃upper branch (8.4 < log (O/H) + 12 < 8.9), then the metallicities of these absorption-selected galaxies span the range between 0.5 and 1.4 Z_☉and would be consistent with the well-known luminosity-metallicity relation for 0.10 < z < 0.45 emission-line galaxies. However, such metallicities would be 0.5-1.0 dex higher than those observed in damped Lyman α systems (DLAs) via absorption-line measurements at similar redshifts. Conversely, the lower R₂₃branch calibration yields metallicities Z∼ 1/7Z_☉, consistent with the DLA absorption metallicities at low redshifts. In this case, the absorption-selected galaxies would lie significantly lower than the luminosity-metallicity relation for emission-line galaxies at z < 0.5. We discuss the implications and possible solutions for each scenario.