Spatially Resolved Velocity Maps of Halo Gas Around Two
  Intermediate-redshift Galaxies
  Absorption-line spectroscopy of multiply-lensed QSOs near a known foreground
galaxy provides a unique opportunity to go beyond the traditional
one-dimensional application of QSO probes and establish a crude
three-dimensional (3D) map of halo gas around the galaxy that records the
line-of-sight velocity field at different locations in the gaseous halo. Two
intermediate-redshift galaxies are targeted in the field around the
quadruply-lensed QSO HE0435-1223 at redshift z=1.689, and absorption
spectroscopy along each of the lensed QSOs is carried out in the vicinities of
these galaxies. One galaxy is a typical, star-forming L* galaxy at z=0.4188 and
projected distance of rho=50 kpc from the lensing galaxy. The other is a
super-L* barred spiral at z=0.7818 and rho=33 kpc. Combining known orientations
of the quadruply-lensed QSO to the two foreground galaxies with the observed
MgII absorption profiles along individual QSO sightlines has for the first time
led to spatially resolved kinematics of tenuous halo gas on scales of 5-10 kpc
at z>0.2. A MgII absorber is detected in every sightline observed through the
halos of the two galaxies, and the recorded absorber strength is typical of
what is seen in previous close QSO--galaxy pair studies. While the
multi-sightline study confirms the unity covering fraction of MgII absorbing
gas at rho < 50 kpc from star-forming disks, the galaxies also present two
contrasting examples of complex halo gas kinematics. Different models,
including a rotating disk, collimated outflows, and gaseous streams from either
accretion or tidal/ram-pressure stripping, are considered for comparisons with
the absorption-line observations, and infalling streams/stripped gas of width
>~ 10 kpc are found to best describe the observed gas kinematics across
multiple sightlines.
