Models of Multi-component Splash Bridges in Face-on Galaxy Disc
  Collisions
  We use an inelastic particle code with shocks and cooling calculated on a
subgrid level to study the gas in direct collisions between galaxy discs. The
interstellar media (ISM) of the discs are modeled with continuous thermal
phases. The models produce many unique structures, collectively called splash
bridges. They range from central bridge discs to swirled sheets, which resemble
those observed in interacting galaxies. These morphologies are sensitive to the
rotation, relative mass, disc offsets and the gas structure in the discs. In
the case of the Taffy galaxies - NGC 12914/15, extensive observations have
revealed radio continuum emitting gas, HI gas, hot X-rays from hot diffuse gas
and more $H_2$ than exists in the Milky Way coexisting in the bridge. The
origins of the $H_2$ and large asymmetric distribution of ISM are not clear. We
show that for small disc impact parameters, multiple phases of ISM with
densities over many orders of magnitude can be removed from their host galaxies
into a Taffy-like bridge. The orientation of the discs initial overlap can have
a great effect on the distributions of each phase of ISM. In some cases, the
models also predict the creation of a possible `dark galaxy,' a large flat
region of dense ISM far from the stellar disc potential of either galaxy.
