Mg II absorption by previously known galaxies at z ≈ 0.5

We have obtained spectra at the Multiple Mirror Telescope of nine QSOs in order to search for Mg II λλ2796, 2803 absorption from intervening galaxies with previously determined redshifts between 0.2 and 0.7. We have detected two Mg II systems with the redshift of known galaxies, including one associated with a cluster of galaxies at z = 0.362. From the lack of detectable Mg II absorption for a large number of other galaxies, we conclude that the galaxies that do absorb must have an effective cross section for absorption at least twice as large in radius as previously thought, in order to account for Mg II absorber statistics. Contrary to previous work, we find that the galaxies with detectable absorption have the same distribution of absolute luminosities as galaxies which show no absorption.