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Title: Optical depth of the universe at radiation-dominated epochs
Authors: Nath, Biman B.
Zdziarski, Andrzej
Keywords: cosmic rays
dark matter
optical thickness
radiation distribution
red shift
compton effect
pair production
relativistic particles
Issue Date: Oct-1990
Publisher: American Astronomical Society
Citation: Astrophysical Journal,1990, Vol. 362,p25
Abstract: If the universe were radiation-dominated at redshifts greater than about 100-1000, e.g., due to the presence of a small fraction of light particles in the dark matter, it would be optically thin in soft gamma-rays up to redshifts of 10,000. This is larger by an order of magnitude than for the matter-dominated universe. X-rays and gamma-rays produced by cosmological high-energy processes are thus potentially observable up to z of about 10,000. Analytical formulas are derived for the optical depths of radiation-dominated universe due to photoionization, Compton scattering, photon-matter pair production, photon-photon scattering, and photon-photon pair production, in interactions with the cosmic thermal background and baryonic matter.
Description: Restricted Access.
ISSN: 0004-637X
1538-4357 (Online)
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Copyright: 1990 The American Astronomical Society
Appears in Collections:Research Papers (A&A)

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