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Session 6 - HII Regions & Massive Star Formation.
Display session, Wednesday, January 07
Exhibit Hall,
We have carried out a survey of Brackett-\gamma emission line of hydrogen (wavelength 2.1655\hbox\mum) in the Galactic plane with the Goddard-Wisconsin cryogenic Fabry-Perot spectrometer. This dual Fabry-Perot spectrometer with a 256x256 InSb detector designed specifically for high spectral resolution (resolving power 10^4) observations of extended objects (field of view of 1\hbox^\circ). The instantaneous velocity range is 200 km\;s^-1. The Brackett-\gamma line is fairly unaffected by the interstellar extinction on the Galactic scale, which makes detecting emission from the distant regions possible.
Observations have been carried out last summer at the IRTF site at Mauna Kea, Hawaii. Spectrometer with an 8 inch telescope was used in non-imaging mode, in which all objects in the field of view equally contribute to the detected spectrum. Fields in the galactic plane at longitudes from -2\hbox^\circ to 34\hbox^\circ in 1\hbox^\circ steps were selected for survey. Most of the selected fields were observed. Velocity range of the observed emission features is from 0 km\;s^-1 to 110 km\;s^-1 (LSR). Typical detected intensities correspond to emission measures of the order of 10^3 cm^-6pc (assuming that emission region fills spectrometer field of view uniformly).
We estimate Ly_c luminosity required to produce the observed Brackett-\gamma emission and discuss the electron density distribution and morphology of the emitting regions.
We appreciate NASA support of this project.
