Astronomy and Astrophysics – Astronomy
Scientific paper
May 1983
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1983phdt........16s&link_type=abstract
Ph.D. Thesis National Aeronautics and Space Administration. Goddard Space Flight Center, Greenbelt, MD.
Astronomy and Astrophysics
Astronomy
16
Background Noise, Flux (Rate), Galactic Nuclei, Heao 2, Luminosity, Maximum Likelihood Estimates, Quasars, X Ray Astronomy, Active Galactic Nuclei, Anisotropy, Brightness Distribution, Cosmic Rays, Fourier Transformation, Galactic Clusters, Spatial Distribution, Spectrum Analysis
Scientific paper
The bright, essentially isotropic, X-ray sky flux above 2 keV yields information on the universe at large distances. However, a definitive understanding of the origin of the flux is lacking. Some fraction of the total flux is contributed by active galactic nuclei and clusters of galaxies, but less than one percent of the total is contributed by the or approximately 3 keV band resolved sources, which is the band where the sky flux is directly observed. Parametric models of AGN (quasar) luminosity function evolution are examined. Most constraints are by the total sky flux. The acceptability of particular models hinges on assumptions currently not directly testable. The comparison with the Einstein Observatory 1 to keV low flux source counts is hampered by spectral uncertainties. A tentative measurement of a large scale dipole anisotropy is consistent with the velocity and direction derived from the dipole in the microwave background. The impact of the X-ray anisotropy limits for other scales on studies of large-scale structure in the universe is sketched. Models of the origins of the X-ray sky flux are reviewed, and future observational programs outlined.
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