2009ApJ...698.1456S

We present 1'' resolution Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations of the 3 mm continuum and 95 GHz CH₃ OH masers toward 14 candidate high-mass protostellar objects (HMPOs). Dust continuum emission is detected toward seven HMPOs, and CH₃ OH masers toward five sources. The 3 mm continuum sources have diameters <2x10⁴ AU, masses between 21 and 1200 M_☉, and volume densities >10⁸/cm3. Most of the 3 mm continuum sources are spatially coincident with compact H II regions and/or water masers, and are presumed to be formation sites of massive stars. A strong correlation exists between the presence of 3 mm continuum emission, 22 GHz H₂ O masers, and 95 GHz CH₃OH masers. However, no 3 mm continuum emission is detected toward ultracompact H II regions lacking maser emission. These results are consistent with the hypothesis that 22 GHz H₂ O masers and CH₃ OH masers are signposts of an early phase in the evolution of an HMPO before an expanding H II region destroys the accretion disk.