Summary: | We report the first detection of the 205 micron 3P1-3P0 [NII] line from a ground based observatory using a direct detection spectrometer. The line was detected and mapped in emission from the Carina star formation region in the Galaxy using the South Pole Imaging Fabry-Perot Interfereometer (SPIFI) on the Antarctic Submillimeter Telescope and Remote Observatory AST/RO at the South Pole. The [NII] line is an important coolant for the diffuse ionized ISM, and (together with the 122 um [NII] line) is an excellent probe of gas density. The [NH] 205 micron line emission peaks at the Carina II HII region, and its strength indicates a low density (n < 30 cm-3) ionized medium. When compared with the ISO [CII] observations of this region, we find about half the [CII] line emission arises from this low density ionized gas as well. The detection of this line demonstrates the utility of Antarctic sites for THz spectroscopy.
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