We present deep WIYN H_alpha SparsePak and DensePak spatially-resolved optical spectroscopy of the dwarf irregular starburst galaxy NGC 1140. The different spatial resolutions and coverage of the two sets of observations have allowed us to investigat
e the properties and kinematics of the warm ionized gas within both the central regions of the galaxy and the inner halo. We find that the position angle of the H_alpha rotation axis for the main body of the galaxy is consistent with the HI rotation axis at PA = 39 deg, but that the ionized gas in the central 20x20 arcsecs (~2x2 kpc) is kinematically decoupled from the rest of the system, and rotates at a PA approximately perpendicular to that of the main body of the galaxy at +40 deg. We find no evidence of coherent large-scale galactic outflows. Instead multiple narrow emission line components seen within a radius of ~1-1.5 kpc, and high [SII]/H_alpha ratios found beyond ~2 kpc implying a strong contribution from shocks, suggest that the intense star formation is driving material outwards from the main star forming zone in the form of a series of interacting superbubbles/shells. A broad component (100<FWHM<230 km/s) to the H_alpha line is identified throughout galaxy disk out to >2 kpc. Based on recent work, we conclude that it is produced in turbulent mixing layers on the surfaces of cool gas knots embedded within the ISM, set up by the feedback from young massive star clusters. Our data suggest a physical limit to the radius where the broad emission line component is significant, and we propose that this limit marks a significant transition point in the development of the galactic outflow, where turbulent motion becomes less dominant. This mirrors what has recently been found in another similar irregular starburst galaxy NGC 1569.
(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.
