  Using N-body and SPH modeling we perform 3D numerical simulations of head-on
collisions between gas rich disk galaxies, including collisions between
counter-rotating disks and off-center collisions. Pure stellar intruders do not
produce gaseous plumes similar to those seen in the Cartwheel and VII Zw466
complexes of interacting galaxies; the presence of gas in an intruder galaxy
and radiative cooling are important for the formation of a gaseous plume
extending from the disk of a target galaxy. A noticeable plume structure can be
formed if the mass of an intruder is a few percent of the mass of the primary.
  The halo of the intruder is stripped in the collision, and dispersed
particles form a broad stellar bridge connecting the two galaxies. The fraction
of the intruder's halo dispersed in the collision depends on the total mass of
the intruder, and low-mass intruders lose most of their mass.
