Cold Fronts from Shock Collisions
  Cold fronts (CFs) are found in most galaxy clusters, as well as in some
galaxies and groups of galaxies. We propose that some CFs are relics of
collisions between trailing shocks. Such a collision typically results in a
spherical, factor ~1.4-2.7 density/temperature discontinuity. These CFs may be
found as far as the virial shock, unlike in other CF formation models. As a
demonstration of this effect, we use one dimensional simulations where halo
reverberations involving periodic collisions between the virial shock and
outgoing secondary shocks exist. These collisions yield a distinctive,
concentric geometric sequence of CFs which trace the expansion of the virial
shock.
