The Optical Structure of the Starburst Galaxy M82. II. Nebular
  Properties of the Disk and Inner-Wind
  (Abridged) In this second paper of the series, we present the results from
optical Gemini-North GMOS-IFU and WIYN DensePak IFU spectroscopic observations
of the starburst and inner wind zones of M82, with a focus on the state of the
T~10^4 K ionized interstellar medium. Our electron density maps show peaks of a
few 1000 cm-3, local small spatial-scale variations, and a fall-off in the
minor axis direction. We discuss the implications of these results with regards
to the conditions/locations that may favour the escape of individual cluster
winds. Our findings imply that the starburst environment is highly fragmented
into a range of clouds from small/dense clumps with low filling factors (<1pc,
n_e>10^4 cm-3) to larger filling factor, less dense gas. The near-constant
state of the ionization state of the ~10^4 K gas throughout the starburst can
be explained as a consequence of the small cloud sizes, which allow the gas
conditions to respond quickly to any changes. We have examined in more detail
both the broad (FWHM 150-350 km/s) line component found in Paper I that we
associated with emission from turbulent mixing layers on the gas clouds, and
the discrete outflow channel identified within the inner wind. The channel
appears as a coherent, expanding cylindrical structure of length >120 pc and
and width 35-50 pc and the walls maintain an approximately constant (but
subsonic) expansion velocity of ~60 km/s. We use the channel to examine further
the relationship between the narrow and broad component emitting gas within the
inner wind. Within the starburst energy injection zone, we find that turbulent
motions (as traced by the broad component) appear to play an increasing role
with height.
