Parsec-scale penetration of UV into molecular clouds: CII 158 micron mapping of W3, NGC 1977, and NGC 2023

Details Parsec-scale penetration of UV into molecular clouds: CII 158 micron mapping of W3, NGC 1977, and NGC 2023 Parsec-scale penetration of UV into molecular clouds: CII 158 micron mapping of W3, NGC 1977, and NGC 2023

Dec 1990

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1990pspu.rept.....h&link_type=abstract

Unknown

Physics

Fine Structure, Infrared Spectra, Interstellar Matter, Line Spectra, Molecular Clouds, Nebulae, Ultraviolet Radiation, Clumps, Cosmic Dust, Emission Spectra, Mapping, Photodissociation, Photons, Radiation Sources, Spatial Distribution

Scientific paper

The spatial distribution of the 158 microns CII fine structure line in the galactic sources W3, NGC 1977, and NGC 2023 is mapped. The emission arises from warm (100 to 300 K), dense photodissociation regions at the surface of molecular gas. In all three sources, the emission extends over parsec scales or greater. For W3 and NGC 1977, where the UV source/molecular cloud geometry presents an edge on view of the variation of CII intensity into the molecular gas, two dimensional models of the CII emission which include the effects of gas clumping and scattering by dust on the transport of UV photons are constructed. The observed CII distribution and intensity is well modeled by a clumpy or filamentary distribution to the molecular gas, with a clump/interclump gas density ratio of 100 or more, which allows deep penetration of carbon ionizing UV photons into the clouds. The penetration of UV into clumped molecular clouds may also explain the extended far IR continuum emission from these sources. The total luminosity of CII emission from a clumpy molecular cloud with adjacent or embedded octave band stars can be as much as an order of magnitude higher than the CII luminosity of a uniform cloud. In addition, the extended penetration of UV into molecular clouds will affect the abundances of atomic and molecular species and increase the fractional ionization of interclump gas and UV illuminated clump surfaces.

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