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| - Emission-line abundances of absorption-selected galaxies at z< 0.5
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| - Abstract. We have obtained optical spectra of four galaxies associated with Mg ii 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 R23 strong-line method. The absolute B-band magnitudes of the galaxies span −20.6 < MB< −18.3. If the metallicities lie on the R23 upper 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 a systems (DLAs) via absorption-line measurements at similar redshifts. Conversely, the lower R23 branch calibration yields metallicities Z ∼ 1/7 Z⊙, 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.
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