Discovery of a transparent sightline at {\rho} < 20 kpc from an
  interacting pair of galaxies
  We report the discovery of a transparent sightline at projected distances of
{\rho} < 20 kpc to an interacting pair of mature galaxies at z = 0.12. The
sightline of the UV-bright quasar PG1522+101 at z = 1.328 passes at {\rho} =
11.5 kpc from the higher-mass galaxy (M_* = 10^10.6 M_Sun) and {\rho} = 20.4
kpc from the lower-mass one (M_* = 10^10.0 M_Sun). The two galaxies are
separated by 9 kpc in projected distance and 30 km/s in line-of-sight velocity.
Deep optical images reveal tidal features indicative of close interactions.
Despite the small projected distances, the quasar sightline shows little
absorption associated with the galaxy pair with a total HI column density it no
greater than log N(HI) = 13.65. This limiting HI column density is already two
orders-of-magnitude less than what is expected from previous halo gas studies.
In addition, we detect no heavy-element absorption features associated with the
galaxy pair with 3-{\sigma} limits of log N(MgII) < 12.2 and log N(OVI) < 13.7.
The probability of seeing such little absorption in a sightline passing at a
small projected distance from two non-interacting galaxies is 0.2%. The absence
of strong absorbers near the close galaxy pair suggests that the cool gas
reservoirs of the galaxies have been significantly depleted by the galaxy
interaction. These observations therefore underscore the potential impact of
galaxy interactions on the gaseous halos around galaxies.
