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Title:
Galaxies and gamma-ray astronomy
Authors:
Bignami, G. F.; Fichtel, C. E.; Hartman, R. C.; Thompson, D. J.
Affiliation:
AA(NASA, Goddard Space Flight Center, Greenbelt, Md.), AB(NASA, Goddard Space Flight Center, Greenbelt, Md.), AC(NASA, Goddard Space Flight Center, Greenbelt, Md.), AD(NASA, Goddard Space Flight Center, Greenbelt, Md.)
Publication:
Astrophysical Journal, Part 1, vol. 232, Sept. 15, 1979, p. 649-658. (ApJ Homepage)
Publication Date:
09/1979
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
BL LACERTAE OBJECTS, COSMOLOGY, GAMMA RAY ASTRONOMY, QUASARS, SEYFERT GALAXIES, ACTIVE GALAXIES, ENERGY SPECTRA, EXTRATERRESTRIAL RADIATION, RADIO GALAXIES, X RAY ASTRONOMY
Comment:
A&AA ID. AAA026.142.504
DOI:
10.1086/157323
Bibliographic Code:
1979ApJ...232..649B

Abstract

The nature of the high-energy spectra of several types of active galaxies and their contribution to the measured diffuse gamma-ray emission between 1 and 150 MeV are considered, using X-ray spectra of active galaxies and SAS 2 data regarding the intensity upper limits to the gamma-ray emission above 35 MeV. It is found that a substantial increase in slope of the photon energy spectrum must occur in the low energy gamma-ray region for Seyfert galaxies, BL Lac objects, and emission line galaxies; the power-law spectra observed in the X-ray range must steepen substantially between 50 keV and 50 MeV. In addition, a cosmological integration shows that Seyfert galaxies, BL Lac objects, and quasars may account for most of the 1-150 MeV diffuse background, even without significant evolution.

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