The Astrophysical Journal · 1985 · 1.3K citations · 0 references
Natural SciencesAstronomyChemistryAstrophysicsInterstellar MediumStellar AstronomyH Ii RegionsInterstellar DustInterstellar Dust EmissionInterstellar GasMolecular CloudsPhotodissociation RegionsChemical Diagnostics Of Interstellar CloudsDust Continuum EmissionDust Emission ModelsDust Grain PropertiesDust In H Ii RegionsMolecular PhotodissociationPhotodissociation ProcessesPhotodissociation Region Chemistry
Models of photodissociation regions apply to dust and gas between molecular clouds and H II regions, and to any neutral cloud illuminated by intense FUV fluxes. The study presents a theoretical parameter analysis of the temperature and chemical structure of dense photodissociation regions and their resulting spectra. The models link observed line and continuum emission to physical parameters—gas density, temperature, elemental and chemical abundances, radiation field, and grain properties—and are applied to OMC‑1 observations. The model explains the high brightness temperature of the C I 609 µm line as emission from the C⁺/C/CO transition region, attributing the discrepancy with earlier models to higher gas‑phase carbon abundance, charge‑exchange reactions with S and SiO, and carbon self‑shielding. Published in ApJ (1985) DOI:10.1086/163111.
view Abstract Citations (1312) References (88) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photodissociation regions. I. Basic model. Tielens, A. G. G. M. ; Hollenbach, D. Abstract A theoretical parameter study of the temperature and chemical structure of dense photodissociation regions and their resultant spectrum is presented. Models are discussed which are relevant not only to the dust and gas between molecular clouds and H II regions, but also apply to any neutral cloud illuminated by intense FUV fluxes. The models relate observed line and continuum emission from these regions to physical parameters such as the gas density and temperature, the elemental and chemical abundances, the local radiation field, and the grain properties. The results are applied to observational data from the OMC-1 region. The model shows that the observed high brightness temperature of the C I 609 microns line can be explained by emission from the C(+)/C/CO transition region. This difference with previous chemical models is due to a higher gas phase elemental abundance of carbon, to the charge exchange reactions of C(+) with S and SiO, and to carbon self-shielding. Publication: The Astrophysical Journal Pub Date: April 1985 DOI: 10.1086/163111 Bibcode: 1985ApJ...291..722T Keywords: Astronomical Models; Gas Ionization; Molecular Clouds; Nebulae; Photodissociation; Abundance; Brightness Temperature; Emission Spectra; Far Ultraviolet Radiation; Fine Structure; Gas Density; Gas Temperature; H Ii Regions; Infrared Spectra; Astrophysics full text sources ADS | data products SIMBAD (5) NED (1) Related Materials (1) Part 2: 1985ApJ...291..747T