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Microturbulence, systematic motions, and line formation in molecular cloudsMicroturbulence and systematic motions are viewed as simplifying assumptions made to facilitate treatment of line formation in molecular clouds, and line intensities calculated in the two approximations are compared to estimate how uncertainties about the actual line-broadening mechanism affect the interpretation of molecular emission lines. For lines formed by two-level molecules in an isothermal homogeneous cloud, the alternative assumptions lead to peak and integrated line intensities which agree within the differences (up to a factor of 3) associated with the ignorance of cloud geometry. New multilevel calculations for CO in the same cloud model bear out the generality of this result. It follows that, within the geometrical uncertainties, the Sobolev (1960) approximation may be used confidently in the numerous applications for which this simple cloud model suffices.
Document ID
19770040310
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
White, R. E.
(NASA Goddard Institute for Space Studies, New York, N.Y.; Smith College, Northampton Mass., United States)
Date Acquired
August 8, 2013
Publication Date
February 1, 1977
Publication Information
Publication: Astrophysical Journal
Subject Category
Astrophysics
Accession Number
77A23162
Funding Number(s)
CONTRACT_GRANT: NSF MPS-73-04949
Distribution Limits
Public
Copyright
Other

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