The Wisconsin H-Alpha Mapper Sky Survey: A First Look At the Global Distribution of Diffuse Ionized Gas in the Milky Way

After a year of observations from its new location on Cerro Tololo, the Wisconsin Hα Mapper (WHAM) has nearly completed survey observations below δ < -30°. This new data combined with the Northern Sky Survey provides the first kinematic, all-sky survey of diffuse Hα from the Milky Way. Aside from many large-scale, locally-ionized regions, much of this emission arises from the Warm Ionized Medium (WIM), a diffuse but thick component of the ISM that extends several kiloparsecs into the Galactic halo. WHAM was designed primarily to study the WIM, delivering a spatially integrated spectrum from a one-degree beam on the sky covering 200 km s-1 with 12 km s-1 spectral resolution. The short exposures of the survey reach sensitivity levels of about 0.1 R (EM 0.2 pc cm-6) and reveal emission toward nearly every direction in the sky. Here, we present our early efforts at reducing this new southern dataset and offer a first look at the global distribution and kinematics of diffuse ionized gas throughout the Galaxy. WHAM and the research presented here are funded by NSF award AST-0607512. We also thank the excellent and responsive staff at CTIO in Chile for helping to keep our remote installation fully operational.