The split in the ancient cold front in the Perseus cluster
  Sloshing cold fronts in clusters, produced as the dense cluster core moves
around in the cluster potential in response to in-falling subgroups, provide a
powerful probe of the physics of the intracluster medium (ICM), and the
magnetic fields permeating it. These sharp discontinuities in density and
temperature rise gradually outwards with age in a characteristic spiral
pattern, embedding into the intracluster medium a record of the minor merging
activity of clusters: the further from the cluster centre a cold front is, the
older it is. Recently it has been discovered that these cold fronts can survive
out to extremely large radii in the Perseus cluster. Here we report on high
spatial resolution Chandra observations of the large scale cold front in
Perseus. We find that rather than broadening through diffusion, the cold front
remains extremely sharp (consistent with abrupt jumps in density) but instead
is split into two sharp edges. These results show that magnetic draping can
suppress diffusion for vast periods of time, around ~5 Gyr, even as the cold
front expands out to nearly half the cluster virial radius.
