The Absorption and Emission Kinematics in thez = 0.7450 MgiiAbsorber toward Q1331+17

(Abridged) We present a comparative analysis of the galaxy emission and QSOabsorption kinematics of a z~0.7450 MgII system and its candidate absorbinggalaxy (G5) located 3.86 arcsecs (28.3 h-1 kpc) from the QSO. We have obtaineda spectrum of the galaxy candidate, previously identified as a luminous edge-ondisk, and detect the [OII] 3727 A doublet at a systemic redshift of z =0.7450. From slit spectroscopy of this galaxy, we find v_rot ~> 210 km/s, andpossibly as large as 350 km/s. Plotted on the same velocity scale, the systemicredshift of the galaxy coincides with the center of the absorption system,although the absorption components span more than 100 km/s in either direction.However, once the sense of the rotation is taken into account, there is noabsorbing gas at the projected velocity of the disk rotation curve. Thisimplies incompatibility with a simple disk scenario. Moreover, a re-analysis ofarchival HST data reveals that the galaxy is only 0.3 L*, considerably lessluminous than previously reported in the literature. Analysis of the absorptionlines shows evidence for superbubbles in the interstellar medium (ISM) of theabsorbing galaxy, based on the striking symmetry between components and largeMgI/MgII and MgI/FeII ratios, indicative of large densities. The large velocityseparations between line pairings, dv ~ 150 km/s indicates that these bubblesmay be powered by OB associations comparable to the largest observed at z=0 andthat the gas is probably enriched to at least 1/10 solar metallicity.Comment: Accepted for publication in Ap