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Physical conditions in photodissociation regions: Application to galactic nucleiInfrared and sub-millimeter observations are used in a simple procedure to determine average physical properties of the neutral interstellar medium in Galactic photodissociation regions as well as in ensembles of clouds which exist in the nuclei of luminous infrared galaxies. The relevant observations include the Infrared Astronomy Satellite (IRAS) infrared continuum measurements, infrared spectroscopy of the fine-structure lines of SiII 35 microns, OI 63 microns, and CII 158 microns, and the 2.6 mm CO (J=1-0) rotational transition. The diagnostic capabilities of the OI 145 microns line is also addressed. Researchers attribute these emission lines as well as the continuum to the atomic/molecular photodissociation region on the surfaces of molecular clouds which are illuminated by strong ultraviolet fields. They use the theoretical photodissociation region models of Tielens and Hollenbach (1985, Ap. J., 291, 722) to construct simple diagrams which utilize line ratios and line to continuum ratios to determine the average gas density n, the average incident far-ultraviolet flux G sub o, and the temperature of the atomic gas T.
Document ID
19910004800
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Wolfire, M. G. (Chicago Univ. IL., United States)
Tielens, A. G. G. M. (NASA Ames Research Center Moffett Field, CA, United States)
Hollenbach, David J. (NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 6, 2013
Publication Date
July 1, 1990
Publication Information
Publication: The Interstellar Medium in External Galaxies: Summaries of Contributed Papers
Subject Category
Astrophysics
Accession Number
91N14113
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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