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Cold dense photoionized universesThis investigation employs a computer code, initially constructed for modeling the evolution of a hot dense intergalactic medium (IGM), to study some properties of a cold dense IGM photoionized by QSOs. Within the observational constraints set by flux measurements in the far-ultraviolet, night sky brightness, and hard X-ray region, and the optical depth limits on various QSO spectra, it determines some allowable scenarios for a range of QSO spectral indices (alpha) and cutoff energies. With H(0) = 50 km/s-Mpc, closure density of an IGM (composed of H and He in their cosmic ratio) is possible only if alpha is greater than or equal to 0.1, a circumstance not likely to prevail; the most probable value, alpha = -0.7, implies an upper limit density about 0.35 of closure, which is somewhat larger than previous estimates. These estimates are substantially independent of whether or not QSOs produce the observed diffuse extragalactic X-ray background; such QSO spectral details are critical, however, in determining the ionization of heavy elements that are expected to contaminate a pure primeval plasma.
Document ID
19800050977
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Sherman, R. D.
(California Institute of Technology, Jet Propulsion Laboratory, Theoretical Physics and Cosmology Group, Pasadena Calif., United States)
Date Acquired
August 10, 2013
Publication Date
April 1, 1980
Publication Information
Publication: Astrophysical Journal
Subject Category
Astrophysics
Accession Number
80A35147
Distribution Limits
Public
Copyright
Other

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