Modeling the chemistry of the dense interstellar clouds. I - Observational constraints for the chemistry

• Published in: The Astrophysical journal Vol. 354; no. 2; pp. 504 - 512
• Main Authors: Federman, S. R., Huntress, W. T., Jr, Prasad, S. S.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS University of Chicago Press 10.05.1990
• Subjects: ALDEHYDES; AMMONIA; Astronomy; Astrophysics; Atomic processes and interactions; CARBON COMPOUNDS; CARBON MONOXIDE; CARBON OXIDES; CHALCOGENIDES; CHEMICAL COMPOSITION; CHEMISTRY; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COSMIC GASES; COSMOCHEMISTRY; Earth, ocean, space; ELECTROMAGNETIC RADIATION; Exact sciences and technology; FLUIDS; FORMALDEHYDE; Fundamental aspects of astrophysics; Fundamental astronomy and astrophysics. Instrumentation, techniques, and astronomical observations; GASES; HYDRIDES; HYDROGEN COMPOUNDS; INTERSTELLAR SPACE; MATHEMATICAL MODELS; MOLECULES; NITROGEN COMPOUNDS; NITROGEN HYDRIDES; NONLUMINOUS MATTER; ORGANIC COMPOUNDS; OXIDES; OXYGEN COMPOUNDS; RADIATIONS; SPACE 640105 > Astrophysics & Cosmology > Galaxies; SPECTRA; ULTRAVIOLET RADIATION; Molecular process; Ammonia; Data analysis; Interstellar cloud; Hydrogen Molecules; Data table; Dark cloud; Carbon monoxide; Column density; Formaldehyde; Interstellar molecule
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/168711

A search for correlations arising from molecular line data is made in order to place constraints on the chemical models of interstellar clouds. At 10 to the 21st H2/sq cm, N(CO) for dark clouds is a factor of six greater than the value for diffuse clouds. This implies that the strength of the UV radiation field where CO shields itself from dissociation is about one-half the strength of the average Galactic field. The dark cloud data indicate that the abundance of CO continues to increase with A(V) for directions with A(V) of 4 mag or less, although less steeply with N(H2) than for diffuse clouds. For H2CO, a quadratic relationship is obtained in plots versus H2 column density. The data suggest a possible turnover at the highest values for A(V). NH3 shows no correlation with H2, C(O-18), HC3N, or HC5N; a strong correlation is found between HC5N and HC3N, indicating a chemical link between the cyanopolyynes.