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Paper: MSX Colors of Radio-Selected HII Regions in the Milky Way
Volume: 317, Milky Way Surveys: The Structure and Evolution of Our Galaxy
Page: 149
Authors: Giveon, U.; Becker, R.H.; Helfand, D.J.; White, R.L.
Abstract: Investigation of the color properties of sources in the MSX catalog reveals two populations - a blue population composed of mainly evolved stars, masers and molecular clouds, and a red population composed mainly H II regions, planetary nebulae, and unclassified radio sources. We compare the MSX catalog to 5 GHz VLA maps of the first quadrant of the Galactic plane 350° < l < 40°, |b| < 0.4°). The comparison resulted in a sample of 491 sources, out of which we estimate 38 to be false counterparts, all of them from the MSX red population. These radio sources with infrared counterparts are found to be extremely bounded to the Galactic plane (scale hight of 12' or ∼ 30 pc), and have thermal continuous radio spectrum (using 1.4 GHz data). These properties suggest that the sample is dominated by H II regions, most of them unclassified so far.
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