THE GREEN BANK ℡ESCOPE H II REGION DISCOVERY SURVEY. II. THE SOURCE CATALOG
Résumé
The Green Bank Telescope (GBT) H II Region Discovery Survey has doubled the number of known H II regions in the Galactic zone 343 degrees \textless= l \textless= 67 degrees with vertical bar b vertical bar \textless= 1 degrees. We detected 603 discrete hydrogen radio recombination line (RRL) components at 9 GHz (3 cm) from 448 targets. Our targets were selected based on spatially coincident mid-infrared and 20 cm radio continuum emission. Such sources are almost invariably H II regions; we detected hydrogen RRL emission from 95% of our target sample. The sensitivity of the GBT and the power of its spectrometer together made this survey possible. Here, we provide a catalog of the measured properties of the RRL and continuum emission from the survey nebulae. The derived survey completeness limit, 180 mJy at 9 GHz, is sufficient to detect all H II regions ionized by single O-stars to a distance of 12 kpc. These recently discovered nebulae share the same distribution on the sky as does the previously known census of Galactic HIT regions. On average, however, the new nebulae have fainter continuum fluxes, smaller continuum angular sizes, fainter RRL intensities, and smaller RRL line widths. Though small in angular size, many of our new nebulae show little spatial correlation with tracers associated with extremely young H II regions, implying that our sample spans a range of evolutionary states. We discovered 34 first quadrant negative-velocity H II regions, which lie at extreme distances from the Sun and appear to be part of the Outer Arm. We found RRL emission from 208 Spitzer GLIMPSE 8.0 mu m “bubble” sources, 65 of which have been cataloged previously. It thus appears that nearly all GLIMPSE bubbles are H II regions and that similar to 50% of all Galactic H II regions have a bubble morphology at 8.0 mu m.