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Cosmic X-ray Background from Self-absorbed Low Luminosity AGNs

Published online by Cambridge University Press:  12 April 2016

Jonathan E. Grindlay  and
Michael Luke
Jonathan E. Grindlay
Affiliation:
Harvard/Smithsonian Center for AstrophysicsCambridge, MAU.S.A.
Michael Luke
Affiliation:
Harvard/Smithsonian Center for AstrophysicsCambridge, MAU.S.A.

Abstract

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A model is proposed for the origin of the diffuse cosmic x-ray background whereby it is primarily due to the contribution of low luminosity active galactic nuclei which are increasingly self-absorbed at low luminosities. Strong self-absorption for low luminosity objects allows the observed background spectrum to be flatter in the ~2-20 keV band than the asymptotic spectrum, assumed to have mean index γ ~ -0.7 up to a high energy cutoff at ~125 keV. The model can account for the spectral shape and intensity of the background spectrum, as well as its possible fluctuations, if the AGN undergo modest density evolution and the bulk of the CXB arises from AGNs at redshifts z ~ 1-3. The model can be tested with AXAF observations of low luminosity AGNs at 5-10 keV and sensitive new hard x-ray observations.

Type
7. Active Galactic Nuclei, Cosmic X-ray Background
Information
International Astronomical Union Colloquium , Volume 115: High Resolution X-ray Spectroscopy of Cosmic Plasmas , 1990 , pp. 276 - 280
Copyright
Copyright © Cambridge University Press 1990

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