Galactic-scale Outflow

A number of studies have concentrated on the minor axis filaments in M82. Imaging observations (e.g., [Lynds & Sandage 1963]; [Ichikawa et al. 1994]) have been directed toward understanding the morphology of the outflow, while spectral studies (e.g., [Burbidge, Burbidge, & Rubin 1964]; [Heckathorn 1972]; [Axon & Taylor 1978]; [Williams, Caldwell, & Schommer 1984]; [Bland & Tully 1988]; [McKeith et al. 1995]) have attempted to parametrize the kinematics of the filaments. The most recent observations detect split emission lines that suggest a pair of expanding bubbles or cones. The exact size and shape of the expanding structures remains a topic of some debate. Additional optical spectroscopy has measured the radial variations of line emission along the outflow (e.g., [Heckman, Armus, & Miley 1990]). Ratios such as [NII]/H$\alpha$ increase with distance from the nuclear starburst, suggesting a gradual change in the gas excitation mechanism. We now investigate these findings in light of the spatial and spectral coverage provided by our Fabry-Perot spectrophotometry.