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Thermal phases of interstellar and quasar gasInterstellar gas may be in a variety of thermal phases, depending on how it is heated and ionized; here a unified picture of the equation of state of interstellar and quasar gas is presented for a variety of such mechanisms over a broad range of temperatures, densities, and column densities of absorbing matter. It is found that for select ranges of gas pressure, photoionizing flux, and heating, three thermally stable phases are allowed: coronal gas (T above 100,000 K); warm gas (T about 10,000 K); and cold gas (T less than 100 K). With attenuation of ultraviolet and X-ray radiation, the cold phase may undergo a transition to molecules. In quasar broad-line clouds, this transition occurs at column density N(H) = about 10 to the 23rd/sq cm and could result in warm molecular cores and observable emission from H2 and OH. The underlying atomic physics behind each of these phase transitions and their relevance to interstellar matter and quasars are discussed.
Document ID
19850041958
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lepp, S.
(Joint Inst. for Lab. Astrophysics Boulder, CO, United States)
Mccray, R.
(Joint Inst. for Lab. Astrophysics Boulder, CO, United States)
Shull, J. M.
(Joint Inst. for Lab. Astrophysics Boulder, CO, United States)
Woods, D. T.
(Joint Inst. for Lab. Astrophysics Boulder, CO, United States)
Kallman, T.
(Joint Institute for Laboratory Astrophysics Boulder, CO, United States)
Date Acquired
August 12, 2013
Publication Date
January 1, 1985
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 288
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
85A24109
Funding Number(s)
CONTRACT_GRANT: NSG-7128
CONTRACT_GRANT: NSF AST-82-16481
Distribution Limits
Public
Copyright
Other

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