NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Chemistry in dynamically evolving cloudsA unified model of chemical and dynamical evolution of isolated, initially diffuse and quiescent interstellar clouds is presented. The model uses a semiempirically derived dependence of the observed cloud temperatures on the visual extinction and density. Even low-mass, low-density, diffuse clouds can collapse in this model, because the inward pressure gradient force assists gravitational contraction. In contrast, previous isothermal collapse models required the low-mass diffuse clouds to be unrealistically cold before gravitational contraction could start. Theoretically predicted dependences of the column densities of various atoms and molecules, such as C and CO, on visual extinction in diffuse clouds are in accord with observations. Similarly, the predicted dependences of the fractional abundances of various chemical species (e.g., CO, H2CO, HCN, HCO(+)) on the total hydrogen density in the core of the dense clouds also agree with observations reported to date in the literature. Compared with previous models of interstellar chemistry, the present model has the potential to explain the wide spectrum of chemical and physical properties of both diffuse and dense clouds with a common formalism employing only a few simple initial conditions.
Document ID
19850043975
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Tarafdar, S. P.
(California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA; Tata Institute of Fundamental Research Bombay, India)
Prasad, S. S.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Huntress, W. T., Jr.
(California Institute of Technology, Jet Propulsion Laboratory, Pasadena CA, United States)
Villere, K. R.
(California, University Santa Cruz, CA, United States)
Black, D. C.
(NASA Ames Research Center Space Science Div., Moffett Field, CA, United States)
Date Acquired
August 12, 2013
Publication Date
February 1, 1985
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 289
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
85A26126
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available