NGC 839: Shocks in an M82-like Superwind
  We present observations of NGC 839 made with the Wide Field Spectrograph
(WiFeS) on the ANU 2.3m telescope. Our data cover a region 25" x 60" at a
spatial resolution of ~1.5". The long axis of the field is aligned with the
superwind we have discovered in this starburst galaxy. The data cover the range
of 3700-7000 {\AA}, with a spectral resolution R~7000 in the red, and R~3000 in
the blue. We find that the stellar component of the galaxy is strongly
dominated by a fast rotating intermediate-age (~400 Myr) A-Type stellar
population, while the gas is concentrated in a bi-conical polar funnel. We have
generated flux distributions, emission line ratio diagnostics and velocity maps
in both emission and absorption components. We interpret these in the context
of a new grid of low-velocity shock models appropriate for galactic-scale
outflows. These models are remarkably well fit to the data, providing for the
first time model diagnostics for shocks in superwinds and strongly suggesting
that shock excitation is largely responsible for the extended LINER emission in
the outflowing gas in NGC 839. Our work may have important implications both
for extended LINER emission seen in other galaxies, as well as in the
interpretation of objects with "composite" spectra. Finally, we present a
scenario for the formation of E+A galaxies based upon our observations of NGC
839, and its relation to M82.
