Chemistry in dynamically evolving clouds

Details Chemistry in dynamically evolving clouds Chemistry in dynamically evolving clouds

Feb 1985

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1985apj...289..220t&link_type=abstract

Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 289, Feb. 1, 1985, p. 220-237. NASA-supported research.

Other

76

Chemical Evolution, Cosmochemistry, Gravitational Collapse, Hydrodynamics, Interstellar Gas, Molecular Clouds, Abundance, Algorithms, Heat Balance, Hydrodynamic Equations, Parameterization, Temperature Distribution

Scientific paper

A 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.

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