Interstellar H2CO. I - Absorption studies, dark clouds, and the cosmic background radiation

Abstract

view Abstract Citations (150) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Interstellar H2CO. I. Absorption studies, dark clouds, and the cosmic background radiation. Evans, N. J., II ; Zuckerman, B. ; Morris, G. ; Sato, T. Abstract The 2ii 212 transition at 2-cm wavelength of interstellar formaldehyde has been observed in absorption against galactic continuum sources and the 2.7 K cosmic background radiation. In addition, the 110 lii transition at 6-cm wavelength of the rare isotopic species H213C06O has been detected in absorption against the cosmic background radiation in at least two clouds. These observations are used to distinguish among the various models for cooling the 6-cm doublet of H212C16O below 2.7 K, and a collisional pumping model is found to be in the best agreement with the observations. In the dark clouds that display this cooling, calculations indicate that the H2 densities are between 102 and 106 , 2 < 10-6, and the value of H213C16O( H212C16O is similar to the terrestrial 12Ct12C ratio. Estimates of the H2CO/H2 ratio in several diverse clouds indicate values of the order of 2-4 x 10-6 Observations toward Cas A indicate that the temperature of the cosmic background radiation at 2-mm wavelength is %< 2.9 K. Subject headings: cosmic background radiation - molecules, interstellar - nebulae Publication: The Astrophysical Journal Pub Date: March 1975 DOI: 10.1086/153424 Bibcode: 1975ApJ...196..433E Keywords: Astronomical Models; Background Radiation; Formaldehyde; Interstellar Matter; Absorption Spectra; Astronomical Catalogs; Clouds; Density Distribution; Electron Transitions; Line Spectra; Molecular Spectra; Optical Pumping; Radial Velocity; Temperature Distribution; Astrophysics full text sources ADS | data products SIMBAD (8)