  We present the following results of photoionization modeling of six
MgII-selected absorption systems, at redshift 0.5 < z 0.9, along lines of sight
toward three quasars: PG 1241+176, PG 1248+401, and PG 1317+274. These are part
of a larger sample of ~20 MgII absorbers at intermediate redshift, that
facilitates a survey of the properties of, and processes active in, the
multiple phases of gas, both in and outside of galaxies. We present new high
resolution ultraviolet spectra from HST/STIS as well as high resolution optical
spectra obtained with HIRES/Keck. Together, these spectra allow simultaneous
study of a variety of ionization states of different chemical elements, with
resolution of the kinematics providing strong constraints on multiphase
properties. The six systems presented here include several that are likely to
arise from lines of sight through disk and halo structures of spiral galaxies.
For these we find that the high ionization gas, traced by CIV is consistent
with coronal structures that resemble that of the Milky Way, along with high
velocity clouds at 100-200 km/s. Another system has relatively weak CIV,
relative to the low ionization absorption, which leads to a discussion of the
circumstances in which a corona might be weak or absent in a galaxy, i.e. an
early-type morphology or low star formation rate. Finally, we present systems
that are examples of single-cloud and multiple-cloud weak MgII absorbers, which
are as a class not likely to be within ~50 kpc of luminous galaxies. Based the
physical conditions inferred from models, we discuss the nature of these types
of systems, which may trace outer regions of galaxies, dwarf galaxy satellites,
or metal-rich regions of the intergalactic medium.
