Astronomy and Astrophysics – Astrophysics
Scientific paper
Nov 1991
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1991ap%26ss.185..195a&link_type=abstract
Astrophysics and Space Science (ISSN 0004-640X), vol. 185, no. 2, Nov. 1991, p. 195-209.
Astronomy and Astrophysics
Astrophysics
2
Abundance, Interstellar Gas, Molecular Clouds, Shock Wave Propagation, Astronomical Models, Gas Cooling, Gas Heating, Hydrodynamic Equations
Scientific paper
The dynamics of the shock waves in a contracting interstellar cloud is examined, with emphasis on the thermal state. The major cooling and heating mechanisms in the postshock are reviewed. The effect of both the abundances of the para- and ortho-H2 and the fractional abundances of C(+), C, and O on the atomic cooling rate are considered. The total rate of cooling by ionic and electronic collisional excitation of C(+), Si(+), and Fe(+) are included. The results indicate that shock waves appear during contraction. The postshock temperature for the two models are, respectively, 3006 K and 2984 K. The density increases by more than three orders of magnitude. This confirms the idea that shock waves can facilitate the progress of the contraction. Under the effect of cooling mechanisms by atoms, molecules, and grains, the shocked medium returns to its initial thermal condition before the occurrence of the shock. At high temperature, the cooling by molecules is vibrational and rotational excitation.
Amin Magdy Y.
El-Nawawy M. S.
El-Shalaby M. A.
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