Deep Chandra observations of NGC 1404: cluster plasma physics revealed
  by an infalling early-type galaxy
  The intracluster medium (ICM), as a magnetized and highly ionized fluid,
provides an ideal laboratory to study plasma physics under extreme conditions
that cannot yet be achieved on Earth. NGC 1404 is a bright elliptical galaxy
that is being gas stripped as it falls through the ICM of the Fornax Cluster.
We use the new {\sl Chandra} X-ray observations of NGC 1404 to study ICM
microphysics. The interstellar medium (ISM) of NGC 1404 is characterized by a
sharp leading edge, 8 kpc from the galaxy center, and a short downstream
gaseous tail. Contact discontinuities are resolved on unprecedented spatial
scales ($0\farcs5=45$\,pc) due to the combination of the proximity of NGC 1404,
the superb spatial resolution of {\sl Chandra}, and the very deep (670 ksec)
exposure. At the leading edge, we observe sub-kpc scale eddies generated by
Kelvin-Helmholtz instability and put an upper limit of 5\% Spitzer on the
isotropic viscosity of the hot cluster plasma. We also observe mixing between
the hot cluster gas and the cooler galaxy gas in the downstream stripped tail,
which provides further evidence of a low viscosity plasma. The assumed ordered
magnetic fields in the ICM ought to be smaller than 5\,$\mu$G to allow KHI to
develop. The lack of evident magnetic draping layer just outside the contact
edge is consistent with such an upper limit.
