THE ANGULAR DISTRIBUTION OF Ly{alpha} RESONANT PHOTONS EMERGING FROM AN OPTICALLY THICK MEDIUM
We investigate the angular distribution of Ly{alpha} photons scattering or emerging from an optically thick medium. Since the evolution of specific intensity I in frequency space and angular space are coupled with each other, we first develop the WENO numerical solver to find the timedependent solutions of the integrodifferential equation of I in frequency and angular space simultaneously. We first show that the solutions with the Eddington approximation, which assume that I is linearly dependent on the angular variable {mu}, yield similar frequency profiles of the photon flux as those without the Eddington approximation. However, the solutions of the {mu} distribution evolution are significantly different from those given by the Eddington approximation. First, the angular distribution of I is found to be substantially dependent on the frequency of the photons. For photons with the resonant frequency {nu}{sub 0}, I contains only a linear term of {mu}. For photons with frequencies at the double peaks of the flux, the {mu}distribution is highly anisotropic; most photons are emitted radially forward. Moreover, either at {nu}{sub 0} or at the double peaks, the {mu} distributions actually are independent of the initial {mu} distribution of photons of the source. This is because the photons withmore »
 Authors:

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 Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States)
 Imaging Sciences and Biomedical Engineering Division, St Thomas Hospital, Kings College London, SE1 7EH (United Kingdom)
 Department of Physics, University of Arizona, Tucson, AZ 85721 (United States)
 Publication Date:
 OSTI Identifier:
 22140114
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Astrophysical Journal; Journal Volume: 772; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANGULAR DISTRIBUTION; ANISOTROPY; APPROXIMATIONS; BEAMS; COLLIMATORS; COSMOLOGY; EMISSION; EVOLUTION; INTEGRODIFFERENTIAL EQUATIONS; MATHEMATICAL SOLUTIONS; PEAKS; PHOTONS; RADIANT HEAT TRANSFER; RESONANCE SCATTERING; SCATTERING; SIMULATION; SPACE; TIME DEPENDENCE