Molecules in galaxies. VI - Diffuse and dense cloud contributions to the large-scale CO emission of the Galaxy

Abstract

view Abstract Citations (127) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Molecules in Galaxies. VI. Diffuse and Dense Cloud Contributions to the Large-Scale CO Emission of the Galaxy Polk, K. S. ; Knapp, G. R. ; Stark, A. A. ; Wilson, R. W. Abstract The integrated (C-12)O and (C-13)O emission ratio is compared for several large regions of the Galactic plane with values for the centers of giant molecular clouds (GMCs) and for the average emission for GMCs. Ratios of 6.7 for the plane, 4.5 for whole GMCs, and 3.0 for GMC centers are obtained. These results show that a significant contribution to the total (C-12)O emission from an ensemble of molecular clouds is made by emitting regions of moderate optical depth compared to a typical GMC. A simple two-component model consisting of diffuse and dense molecular clouds is compared with these data and suggests that the application of a conversion factor between CO intensity and H2 column density derived for GMCs will overestimate the H2 mass of a cloud ensemble or a galaxy. The conversion between CO emission and total H2 column density in the Galaxy is 2 x 10 to the 20th/sq cm, in reasonable agreement with values obtained using the gamma-ray calibration. Publication: The Astrophysical Journal Pub Date: September 1988 DOI: 10.1086/166667 Bibcode: 1988ApJ...332..432P Keywords: Astronomical Spectroscopy; Carbon Monoxide; Emission Spectra; Interstellar Gas; Milky Way Galaxy; Molecular Clouds; Galactic Radiation; Gas Density; Line Spectra; Molecular Diffusion; Astrophysics; INTERSTELLAR: ABUNDANCES; INTERSTELLAR: MATTER; INTERSTELLAR: MOLECULES full text sources ADS | Related Materials (5) Part 1: 1986ApJ...305..823R Part 2: 1986AJ.....91..517R Part 3: 1986ApJ...310..660S Part 4: 1987AJ.....94...54K Part 5: 1987ApJ...322...64S