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Published June 20, 2009 | Published
Journal Article Open

Testing the Evolutionary Sequence of High-Mass Protostars with CARMA


We present 1" resolution Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations of the 3 mm continuum and 95 GHz CH_3OH masers toward 14 candidate high-mass protostellar objects (HMPOs). Dust continuum emission is detected toward seven HMPOs, and CH3OH masers toward five sources. The 3 mm continuum sources have diameters < 2 × 10^4 AU, masses between 21 and 1200 M⊙, and volume densities > 10^8 cm^(–3). 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 H_2O masers, and 95 GHz CH_3OH 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 H_2O masers and CH_3OH masers are signposts of an early phase in the evolution of an HMPO before an expanding H II region destroys the accretion disk.

Additional Information

© 2009 The American Astronomical Society. Received 2008 December 19; accepted 2009 April 15; published 2009 June 1. We thank the referee for improving the clarity and increasing the scope of this paper. We thank the CARMA staff, students, and postdocs for their help in making these observations. We acknowledge support from the Owens Valley Radio Observatory, which is supported by the National Science Foundation through grant AST 05-40399. Support for CARMA construction was derived from the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the Associates of the California Institute of Technology, the states of California, Illinois and Maryland, and the National Science Foundation. Ongoing CARMA development and operations are supported by the National Science Foundation under a cooperative agreement, and by the CARMA partner universities. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.

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Published - Schnee2009p4594Astrophys_J.pdf


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