Studies of Massive Star Formation in the Milky Way
Professor James Jackson, his students, and collaborators have developed a median-filter subtraction technique to suppress unrelated foreground and background emission along the line of sight through the Milky Way Galaxy in order to isolate emission from star-forming cores. Using this method with the Herschel Space Telescope, they have shown that the dust temperatures correlate in the expected way with the evolutionary state of the star-forming cores. Based on the morphology in Spitzer Space Telescope infrared images, they classify clumps as “pre-stellar” (dark at all mid-IR wavelengths), “protostellar” (IR dark except for point sources at wavelengths of roughly 24 mm or longer; coupled with “green fuzzy” or “extended green object” emission at 4.5 mm that indicates outflows), and “H II regions” (bright extended 8 mm emission from PAHs and extended emission at about 24 mm and longer). The pre-stellar clumps are the coldest, the protostellar clumps are warmer, and the H II region clumps are the warmest. The group has produced robust maps of dust temperatures, column densities, and submillimeter-wave/far-infrared luminosities for every core in their survey.