On the Spatial and Kinematic Distributions of MgiiAbsorbing Gas in (Z) ∼0.7 Galaxies

(Abridged) We present HIRES/Keck spectra having resolution 6 km/s of Mg II2796 absorption profiles which arise in the gas associated with 15 identifiedgalaxies over the redshift range 0.5 < z < 0.9. Using non-parametric rankcorrelation tests, we searched for correlations of the absorption strengths,saturation, and line-of-sight kinematics with the galaxy redshifts, rest frameB and K luminosities, rest colors, and impact parameters D. We found nocorrelations at the 2.5-sigma level between these properties. Of primarysignificance is the fact that the QSO-galaxy impact parameter apparently doesnot provide the primary distinguishing factor by which absorption propertiescan be characterized. The galaxy absorption properties exhibit a large scatter,which, we argue, is suggestive of a picture in which the gas arises from avariety of on-going dynamical events. Inferences from our study include: (1)The spatial distribution of absorbing gas in galaxies does not appear to followa simple galactocentric functional dependence. (2) A single systematickinematic model apparently cannot describe the observed velocity spreads in theabsorbing gas. It is more that a heterogeneous population of sub-galaxy scalestructures are giving rise to the observed cloud velocities. (3) The absorbinggas spatial distribution and kinematics may depend upon gas producing eventsand mechanisms that are recent to the epoch at which the absorption isobserved. These distributions likely change over a few Gyr timescale. Basedupon these inferences, we note that any evolution in the absorption gasproperties over a larger redshift range should be directly quantifiable from alarger dataset of high-resolution absorption profiles.