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Published April 15, 1981 | Published
Journal Article Open

Temperatures of galactic molecular clouds showing CO self-absorption


The CO J=2- l line has been observed and, in most cases, mapped in 10 star-forming molecular clouds (W3, NGC 1333, NGC 2071, Mon R2, CRL 961, p Oph, W49N, W51A, DR 21, and Cep A). The CO J = 3-2 line has been observed in W3 and DR 21. The CO lines from all of these sources are strongly self-absorbed. By comparing our results with published CO (1-0) line profiles, we find that large corrections to the temperatures of the cloud cores, as measured by the CO (1-0) lines, are required. The corrections for self-absorption bring the CO brightness temperatures into closer agreement with the grain temperatures inferred from far-infrared photometry. The absorbing gas appears to have a variety of geometrical relationships with the absorbed 'background' gas for this group of sources; in one or two cases there may be no physical connection between the absorbed and absorbing regions. For some CO sources, the combined CO data indicate the presence of velocity gradients; however, whether these are due to expansion or collapse cannot be decided on the basis of the presently available data.

Additional Information

© 1981 American Astronomical Society. Received 1980 August 20; accepted 1980 October 22. We thank the staff of the Owens Valley Radio Observatory and of the Palomar Observatory for their help in support of this work. Research in millimeter-wave astronomy at the California Institute of Technology is supported by the National Science Foundation via grant AST-79-16815. Part of this work was supported by NASA grant NGL 05-002-207.

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Published - 1981ApJ___245__512P.pdf


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