  We present numerical simulations of off-center collisions between galaxy
clusters made using a new hydrodynamical code based on the piecewise-parabolic
method (PPM) and an isolated multigrid Poisson solver. We have performed three
gas-only high-resolution simulations of collisions between equal-mass clusters
with different values of the impact parameter (0, 5, and 10 times the core
radius). With these simulations we have studied the observational appearance of
the merging clusters and the variation in equilibration time, luminosity
enhancement during the collision, and structure of the merger remnant with
varying impact parameter. Observational evidence of an ongoing collision is
present for 1-2 sound crossing times after the collision, but only for special
viewing angles. The remnant actually requires at least five crossing times to
reach virial equilibrium. Since the sound crossing time can be as large as 1-2
Gyr, the equilibration time can thus be a large fraction of the age of the
universe. The final merger remnant is very similar for impact parameters of
zero and five core radii. It possesses a roughly isothermal core, with central
density and temperature twice the initial values. Outside the core the
temperature drops as r^-1, and the density roughly as r^-3.8. The core radius
shows a small increase due to shock heating during the merger. For an impact
parameter of ten core radii the core of the remnant possesses a more flattened
density profile, with a steeper dropoff outside the core. In both off-center
cases the merger remnant rotates, but only for the ten-core-radius case does
this appear to have an effect on the structure of the remnant.
