DENSE PHOTODISSOCIATION REGIONS (PDRs)
نویسندگان
چکیده
منابع مشابه
Non-equilibrium Photodissociation Regions: Ionization-dissociation Fronts
We discuss the theory of coupled ionization{dissociation fronts produced when molecular clouds are exposed to < 1110 A radiation from hot stars. A steady, composite structure is developed, which generally includes an ionized outtow away from the cloud, an ionization front, a layer of photodissociated gas, a photodissociation front, and a shock wave preceding the photodissociation front. We show...
متن کاملPhotoevaporation of Clumps in Photodissociation Regions
We present the results of an investigation of the effects of Far Ultraviolet (FUV) radiation (6.0eV < hν < 13.6eV) from hot early type OB stars on clumps in star-forming molecular clouds. Clumps in FUV-illuminated regions (or pho-todissociation regions or PDRs) undergo external heating and photodissociation as they are exposed to the FUV field, resulting in a loss of cold, molecular clump mass ...
متن کاملSilicon chemistry in PDRs
We consider the chemistry of silicon in photo– dissociation regions (PDRs), with special attention to the available observations of the Orion Bar. We focus on the “paradox” that fine structure emission of singly ionized silicon (Si+) is known to be strong from such regions, whereas silicon in molecular form (and in particular SiO) is absent. We consider a number of possible explanations of this...
متن کاملMetallicity Effects in Pdrs
Almost all properties of a photodissociation region (PDR) depend on its metallicity. The heating and cooling efficiencies that determine the temperature of the gas and dust, the dust composition, as well as the elemental abundances that influence the chemical structure of the PDR are just three examples that demonstrate the importance of metallicity effects in PDRs. PDRs are often associated wi...
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The presence of methyl alcohol or methanol (CH3OH) in several astrophysical environments has been characterized by its high abundance that depends on both the production rate and the destruction rate. In the present work, the photoionization and photodissociation processes of methanol have been experimentally studied, employing soft X-ray photons (100-310 eV) from a toroidal grating monochromat...
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ژورنال
عنوان ژورنال: Annual Review of Astronomy and Astrophysics
سال: 1997
ISSN: 0066-4146,1545-4282
DOI: 10.1146/annurev.astro.35.1.179