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A.G. Gibb (UMD), F. Wyrowski (MPIfR, Bonn), L.G. Mundy (UMD), M.A. Thompson (Univ of Kent, UK)
We have used the 10-element BIMA interferometer to observe a sample of 9 ultracompact HII regions in the 3-mm lines of N2H+, CH3OH, C34S, CH3CN, C18O and 3-mm continuum. The sample was chosen to include sources which show extended submillimetre dust emission. We detected 50 massive cores, most of which are previously unknown. The majority also have no signposts of current star formation such as embedded infrared or radio sources and water or methanol masers. There is a good correlation between the submillimetre dust continuum peaks and the N2H+ emission, while the N2H+ also traces a number of infrared-dark cores. For those cores mapped in both N2H+ and C18O, 21% have weak or no C18O emission. These cores show evidence for CO depletion, and may therefore be in the early stages of forming a massive star.
Research with BIMA is supported by grant AST-9981289 from NSF.