A search for H II regions embedded in intermediate-mass molecular clouds

The results of a radio-continuum survey of embedded H II regions of a number of relatively nearby molecular clouds of moderate size are reported. A number of flat-spectral-index sources were found, for which flux densities were measured at 1.3, 2.8, and 9 cm. The relationship of these sources with t...

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Bibliographic Details
Published in:The Astronomical journal 1989-01, Vol.97, p.172-181
Main Authors: Moriarty-Schieven, G. H., Hughes, V. A., MacLeod, G. C.
Format: Article
Language:English
Online Access:Get full text
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Summary:The results of a radio-continuum survey of embedded H II regions of a number of relatively nearby molecular clouds of moderate size are reported. A number of flat-spectral-index sources were found, for which flux densities were measured at 1.3, 2.8, and 9 cm. The relationship of these sources with their associated molecular clouds is discussed. It is concluded that (1) the star-forming efficiency of these clouds is 2-3 percent, and possibly as high as 5 percent; (2) early-type stars can form in molecular clouds with mass more than 10,000 solar; (3) studies that predict the most massive star that can form in a molecular cloud of a given mass may be underestimating the mass of the cloud because of selection effects; and (4) an energy-balance criterion for collapse of a molecular clouds, similar to the Jeans criterion but using the turbulence kinetic energy of the cloud rather than the thermal energy, may predict where massive stars form. (C.D.)
ISSN:0004-6256
DOI:10.1086/114966