2007MNRAS.376..673M

A correlation between the metallicity, [M/H], and rest-frame Mgii equivalent width, W^λ2796_r, is found from 49 damped Lyα absorbers (DLAs) and strong sub-DLAs drawn from the literature over the redshift range 0.2 < z_abs< 2.6. The correlation is significant at 4.2σ and improves to 4.7σ when the mild evolution of [M/H] with redshift is taken into account. Even when including only the 26 DLAs (i.e. excluding sub-DLAs) which have Zn-metallicities and W^λ2796_r> 0.7Å, the correlation remains at >3σ significance. Since the Mgii λ2796 transition is predominantly saturated in DLAs (which always have W^λ2796_r greater than 0.3Å), W^λ2796_r is far more sensitive to the kinematic spread of the metal velocity components across the absorption profile than it is to [M/H]. Thus, the observed [M/H]-W^λ2796_rcorrelation points to a strong link between the absorber metallicity and the mechanism for producing and dispersing the velocity components. We also note that approximately half of the 13 known H₂ absorbers have very high W^λ2796_r and very broad velocity structures which show characteristics usually associated with outflows. Follow-up ultraviolet- and blue-sensitive high-resolution spectra of high-W^λ2796_rsystems, initially identified in low-resolution spectra, may therefore yield a large number of new H₂discoveries.