Radiation transport and non-LTE analysis of interstellar molecular lines. II - Carbon monosulfide

Abstract

view Abstract Citations (24) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radiation transport and non-LTE analysis of interstellar molecular lines. II. Carbon monosulfide. Liszt, H. S. ; Leung, C. M. Abstract We present numerical solutions to the coupled equations of radiative transfer and statistical equilibrium in the rotational transitions of carbon monosulfide (CS), similar to those in our earlier paper on carbon monoxide. Static, spherical, and microturbulent models are constructed over a wide range in density, abundance, and temperature, and the results are compared with observations of massive clouds near H ii regions and of dark dust clouds and globules. The optical depths found for CS are quite small in all cases, typically < 2, and the J = 1 0 line is found to be a weak maser in the rarer isotopic species in some denser clouds. No single value of the abundance fits all massive clouds, but typical central densities and relative abundances are 5 x l0 < < 2 x l0 , 2 x 10-10 < nos/ < 2 x l0- . Mean densities are a factor 5-10 lower because strong density gradients are required to reproduce the small spatial extent of the observed CS emission. The observations are dominated by instrumental effects, and it is difficult to determine whether source-to-source abundance variations actually exist. In the four globules which show emission in the two lowest transitions, ncs! 5-10 >c 10-10 and 2 5-20 x l0 . The observational results for L134 and the Taurus dark cloud are greatly discrepant and cannot be modeled for any reasonable choice of parameters. Subject headings: interstellar: abundances - interstellar: molecules Publication: The Astrophysical Journal Pub Date: December 1977 DOI: 10.1086/155693 Bibcode: 1977ApJ...218..396L Keywords: Abundance; Carbon Compounds; Interstellar Matter; Molecular Spectra; Radiative Transfer; Spectrum Analysis; Sulfides; Electron Transitions; Hydrogen Clouds; Molecular Rotation; Thermodynamic Equilibrium; Astrophysics full text sources ADS |