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Observations of molecular and atomic gas in photodissociation regionsDense gas at the ionized/neutral boundaries of molecular clouds illuminated by far-UV photons plays an important role in the appearance of the neutral interstellar medium. It also is a laboratory for the study of UV-photochemistry and of a number of heating and cooling phenomena not seen elsewhere. Fine structure lines of neutral and low ionization potential species dominate the cooling in the outer part of the photodissociation regions. Observations of these lines show that the regions are dense and highly clumped. Observations of H2 and CO show that heating by UV photons plays a significant role in the excitation of molecular lines near the H II/neutral boundary. Warm CO is more abundant in these regions than predicted by the standard theoretical models. Optical reflection nebulas provide an ideal laboratory for the study of photodissocciation region phenomena.
Document ID
19900045352
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Jaffe, D. T.
(Texas Univ. Austin, TX, United States)
Howe, J. E.
(Texas, University Austin, United States)
Date Acquired
August 14, 2013
Publication Date
September 1, 1989
Publication Information
Publication: Revista Mexicana de Astronomia y Astrofisica
Volume: 18
ISSN: 0185-1101
Subject Category
Astrophysics
Accession Number
90A32407
Funding Number(s)
CONTRACT_GRANT: NSF AST-88-15801
CONTRACT_GRANT: NAG2-419
Distribution Limits
Public
Copyright
Other

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