ON THE SPATIAL AND KINEMATIC DISTRIBUTIONS OF MG-II ABSORBING GAS IN [Z]SIMILAR-TO-0.7 GALAXIES

We present HIRES/Keck spectra having resolution similar to 6 km s(-1) of Mg II lambda 2796 absorption profiles that arise in the gas believe d to be associated with 15 identified galaxies over the redshift range (0.5 less than or equal to z less than or equal to 0.9). These galaxi es have measured redshifts consistent with those seen in absorption. U sing nonparametric rank correlation tests, we searched for correlation s of the absorption strengths, saturation, and line-of-sight kinematic s with the galaxy redshifts, rest frame B and K luminosities, rest (B- K) colors, and impact parameters D. We found no correlations at the 2. 5 sigma level between the measured absorption properties and galaxy pr operties. Of primary significance is the fact that the QSO-galaxy impa ct parameter apparently does not provide the primary distinguishing fa ctor by which absorption properties can be characterized. The absorpti on properties of Mg II selected galaxies exhibit a large scatter, whic h, we argue, is suggestive of a picture in which the gas in galaxies a rises from a variety of ongoing dynamical events. Inferences from our study include the following: (1) The spatial distribution of absorbing gas in and around galaxies does not appear to follow a simple galacto centric functional dependence, since the gas distribution is probably highly structured. (2) A single systematic kinematic model apparently cannot describe the observed velocity spreads in the absorbing gas. It is more likely that galaxy/halo events giving rise to absorbing gas e ach exhibit their own systematic kinematics, so that a heterogeneous p opulation of subgalaxy scale structures are giving rise to the observe d cloud velocities. (3) The absorbing gas spatial distribution and ove rall kinematics may depend upon gas-producing events and mechanisms th at are recent to the epoch at which the absorption is observed. In any given galaxy, these distributions likely change over a similar to few Gyr timescale (few dynamical times of the absorbing clouds), which pr ovides one source for the observed scatter in the absorption propertie s. Based upon these inferences, we note that any evolution in the abso rption gas properties over the wider redshift range (0.4 less than or equal to z less than or equal to 2.2) should be directly quantifiable from a larger data set of high-resolution absorption profiles.