Observations of Zn II, Cr II, Fe II, and Ca II in the damped lyman-alpha absorber at z = 0.692 toward 3C 286

We report the first observations of Zn II and Cr II in a low-redshift damped Lyα QSO absorption-line system. Using the N(Zn II)/N(H I) ratio as a probe of the metallicity and AT(Cr II)/N(Zn II) and N(Fe II)/ N(Zn II) as measures of the dust content, we find that the heavy-element abundances in the z = 0.692 absorber toward the QSO 3C 286 are ≈6% solar and that the dust-to-gas ratio is ≈5% of that of the Galactic disk. The fact that these values are consistent with those of the four high-redshift (z > 1.9) damped systems whose Zn and Cr abundances have been examined quantitatively to date suggests that if these systems represent a single population of galaxies, they are evolving slowly, if at all. Furthermore, since the redshift of the 3C 286 system corresponds approximately in time to the epoch of the Sun's formation, the disparity in their metallicities argues strongly that this damped Lyα absorber, at least, is not representative of a galactic disk evolving on a coeval basis with the Milky Way.