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A New Catalog of Radio Compact HII Regions in the Milky Way

Uriel Giveon·Robert H. Becker·David J. Helfand·Richard L. White
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Abstract

We utilize new VLA Galactic plane catalogs at 5 and 1.4 GHz covering the first Galactic quadrant (350<l<42, |b|<0.4) in conjunction with the MSX6C Galactic plane catalog to construct a large sample of ultra-compact HII regions. A radio catalog of this region was first published by Becker et al. (1994), but we have added new observations and re-reduced the data with significantly improved calibration and mosaicing procedures, resulting in a tripling of the number of 5 GHz sources detected. Comparison of the new 5 GHz catalog and the MSX6C Galactic plane catalog resulted in a sample of 687 matches, out of which we estimate only 15 to be chance coincidences. Most of the matches show red MSX colors and a thermal radio spectrum. The scale height of their Galactic latitude distribution is very small (FWHM of 16' or ~40 pc). These properties suggest that the sample is dominated by young ultra-compact HII regions, most of which are previously uncataloged. High reliability and low reliability source lists are available for download with the paper.

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Uriel Giveon, Robert H. Becker, David J. Helfand, Richard L. White. 2004-10-15. A New Catalog of Radio Compact HII Regions in the Milky Way. https://doi.org/10.1086/426360

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