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Title:
The energetics of molecular clouds. II - The S140 molecular cloud
Authors:
Blair, G. N.; Evans, N. J., II; Vanden Bout, P. A.; Peters, W. L., III
Affiliation:
AA(Department of Astronomy and McDonald Observatory, The University of Texas at Austin, USA and Netherlands Foundation for Radio Astronomy), AB(Department of Astronomy and McDonald Observatory, The University of Texas at Austin, USA), AC(Department of Astronomy and McDonald Observatory, The University of Texas at Austin, USA), AD(Electrical Engineering Research Laboratory, The University of Texas at Austin, USA)
Publication:
Astrophysical Journal, Part 1, vol. 219, Feb. 1, 1978, p. 896, 897, 899-913. (ApJ Homepage)
Publication Date:
02/1978
Category:
Astrophysics
Origin:
STI; NRAO
NASA/STI Keywords:
ABUNDANCE, GAS HEATING, INTERSTELLAR CHEMISTRY, MOLECULAR SPECTRA, NEAR INFRARED RADIATION, NEBULAE, ASTRONOMICAL MODELS, CARBON MONOXIDE, COSMIC DUST, GAS DENSITY, GAS TEMPERATURE, LINE SHAPE, RADIATIVE TRANSFER, REACTION KINETICS
Comment:
A&AA ID. AAA021.131.021
DOI:
10.1086/155853
Bibliographic Code:
1978ApJ...219..896B

Abstract

Techniques of analysis which allow estimates of kinetic temperature, gas density, gas cooling rate, and dust cooling rate are applied to the S140 molecular cloud. Maps of this cloud in various molecular lines are examined which reveal the existence of a strong temperature and density peak near the H-alpha rim and the presence of a strong near-IR source very near that peak. This source is found to have an energy distribution which is very similar to that of the Becklin-Neugebauer object, including the silicate feature at 9.5 microns. The heating and cooling rates for the gas and dust in S140 are estimated, and the predicted cooling rate for dust is shown to be much greater than that for gas. The molecular-line observations are compared with a spherical large-velocity-gradient trapping calculation. An optimum cloud model is developed which indicates that: (1) (C-13)O, HCO(+), and H2CO are about 10 times less abundant in S140 than in dark clouds; (2) the HCN abundance is approximately 4 times the H2CO abundance in S140, compared with roughly equal values in dark clouds; and (3) the (C-13)O/C(O-18) ratio is consistent with terrestrial isotope ratios.

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