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High-energy galactic gamma radiation from cosmic rays concentrated in spiral armsA model for the emission of high-energy (exceeding 100 Mev) gamma-rays from the galactic disk has been developed and compared with recent SAS-2 observations. In the calculation, it is assumed that (1) the high energy galactic gamma-rays result primarily from the interaction of cosmic rays with galactic matter, (2) the cosmic-ray density is proportional to the matter density on the scale of galactic arms, and (3) the matter in the Galaxy is distributed in a spiral pattern consistent with density-wave theory and experimental data on the matter distribution that is available, including the 21-cm H I line emission, continuum emission from H II regions, and data currently being used to estimate the H2 density. The calculated galactic-longitude distribution of gamma rays is in good agreement with the SAS-2 observations in relative shape and absolute flux. As a corollary, the nonuniform cosmic-ray distribution of this model tends to support the galactic origin of the fraction of cosmic rays which is important in the production of high-energy photons. Modifications of the basic model show that the gamma-ray flux is relatively sensitive to large variations of the assumed distribution of molecular hydrogen in the Galaxy.
Document ID
19750053850
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Bignami, G. F.
Fichtel, C. E.
Kniffen, D. A.
Thompson, D. J.
(NASA Goddard Space Flight Center Greenbelt, Md., United States)
Date Acquired
August 8, 2013
Publication Date
July 1, 1975
Publication Information
Publication: Astrophysical Journal
Volume: 199
Subject Category
Space Radiation
Accession Number
75A37922
Distribution Limits
Public
Copyright
Other

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