Models of interstellar clouds. I. The Zeta Ophiuchi cloud

Journal Article · Fri Jul 01 04:00:00 EDT 1977 · Astrophys. J., Suppl. Ser.; (United States)

DOI:https://doi.org/10.1086/190455· OSTI ID:7090864

Black, J H; Dalgarno, A

Techniques for constructing detailed models of diffuse interstellar clouds are described. The models are designed to reproduce the observational data on the abundance and rotational excitation of H/sub 2/, the abundances of other molecules and of atomic ions, and the fine-structure populations of carbon. Results are presented for the zeta Ophiuchi cloud. A model with two components accounts adequately for all the available observational data. The temperature and total density are respectively 110 K and 500 cm/sup -3/ in the outer region and 22 K and 2500 cm/sup -3/ in the inner core. The measured abundance of CH can be reproduced by postulating a rate coefficient of 5 x 10/sup -16/ cm/sup 3/ s/sup -1/ at 22 K for the radiative association reaction C/sup +/+H/sub 2/..-->..CH/sub 2//sup +/+hv. The measured abundances of HD and OH can be reproduced by an ionization rate of 1.6 x 10/sup -17/ s/sup -1/ and a rate coefficient of 5 x 10/sup -10/ cm/sup 3/s/sup -1/ for the reaction O/sup +/+H..-->..O+H/sup +/. The abundances of CO and CN are reproduced by using plausible estimates of their photo-dissociation rates, but the chemical scheme seriously underestimates the abundance of CH/sup +/. The concentrations of other simple molecules are predicted. The molecule C/sub 2/ may be detectable. The known heating sources appear adequate to maintain the inferred temperatures.

• Research Organization: School of Physics and Astronomy, University of Minnesota
• OSTI ID: 7090864
• Journal Information: Astrophys. J., Suppl. Ser.; (United States), Journal Name: Astrophys. J., Suppl. Ser.; (United States) Vol. 34:3; ISSN APJSA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
COSMIC GASES
ELECTROMAGNETIC RADIATION
FLUIDS
FUNCTIONS
GASES
INTERSTELLAR GRAINS
INTERSTELLAR SPACE
LINE WIDTHS
MOLECULES
NEBULAE
NUCLEAR REACTIONS
PARTICLES
RADIATIONS
SPACE
SPECTRAL FUNCTIONS
ULTRAVIOLET RADIATION