Bibcode
Beckman, J. E.
Bibliographical reference
IN: Progress in stellar spectral line formation theory; Proceedings of the Advanced Research Workshop, Trieste, Italy, September 4-7, 1984 (A86-37976 17-90). Dordrecht, D. Reidel Publishing Co., 1985, p. 389-405.
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1985
Citations
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Refereed citations
0
Description
A summary is presented of the physical considerations governing line
formation in molecular clouds with kinetic temperatures in the range
from 5 to 100 K and hydrogen number densities in the range from 100 to
one million per cubic centimeter. An exposition of the classical Sobolev
formulation due to Goldreich and Kwan (1973) is followed by results of a
simple microturbulent model with partial redistribution due to Deguchi
and Kwan. It is explained how line formation theory in molecular clouds
is in a somewhat unsatisfactory state. Large velocity gradient models
can account for the observed line shapes, but imply collapse times that
are unreasonably short (less than 10 to the 6 years). Microturbulent
models give unrealistic self-absorbed CO profiles, which are scarcely
improved using transfer theory which includes partial redistribution. It
is hoped that the review will serve to draw the attention of
practitioners of line transfer theory in stellar atmospheres to a key
problem in interstellar physics that requires further attention.