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Paper: Surveying the Galaxy with WHAM
Volume: 317, Milky Way Surveys: The Structure and Evolution of Our Galaxy
Page: 186
Authors: Reynolds, R.J.; Haffner, L.M.; Madsen, G.J.; Tufte S.L.
Abstract: The Wisconsin H-Alpha Mapper (WHAM) has provided for the first time an Hα survey of the distribution and kinematics of the diffuse interstellar H II in the Milky Way that is comparable to earlier 21 cm surveys of the H I. The WHAM survey, consisting of 37,565 spectra north of declination -30°, reveals wide-spread interstellar ionization spanning an area from well outside the solar circle to the inner Galaxy. Diffuse ionized gas and filaments reach more than 1000 pc from the disk. Near the Galactic midplane the H II appears to have little relationship to the H I; however, at higher Galactic latitudes the WHAM survey reveals a close relationship, both kinematically and spatially, between the diffuse H II and “warm” (i.e., broad 21 cm component) H I clouds, including the distinct complexes of H I clouds at intermediate and high velocities. A survey of the nebular [N II] and [S II] lines over more limited regions of the sky has also made it possible to map variations in the excitation and ionization of this gas.
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