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Hydrostatic Models of Molecular Clouds

Published online by Cambridge University Press:  14 August 2015

T. De Jong ,
A. Dalgarno  and
W. Boland
T. De Jong
Affiliation:
∗Astronomical Institute, 1018 WB Amsterdam, The Netherlands
A. Dalgarno
Affiliation:
†Center for Astrophysics, Cambridge, MA 02138, USA
W. Boland
Affiliation:
∗Astronomical Institute, 1018 WB Amsterdam, The Netherlands †Center for Astrophysics, Cambridge, MA 02138, USA

Extract

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It is customary to convert observed brightness temperatures of molecular lines to molecular column densities by assuming some excitation temperature to describe the population of the energy levels of the molecule. Observers often speak about “abundances” after dividing these column densities by the dimension of the cloud that is being studied. This procedure can be misleading because the level populations are usually not well characterized by one single excitation temperature and because clouds are probably quite centrally condensed. Some molecules are formed preferentially at high densities in the opaque cores of clouds, others reach their maximum abundance in the moderately shielded much less dense outer regions of clouds.

Type
Research Article
Information
Symposium - International Astronomical Union , Volume 87: Interstellar Molecules , 1980 , pp. 177 - 181
Copyright
Copyright © Reidel 1980 

References

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