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Title: BALANCING THE COSMIC ENERGY BUDGET: THE COSMIC X-RAY BACKGROUND, BLAZARS, AND THE COMPTON THICK ACTIVE GALACTIC NUCLEUS FRACTION

Abstract

At energies approx>2 keV, active galactic nuclei (AGNs) are the source of the cosmic X-ray background (CXB). For AGN population synthesis models to replicate the peak region of the CXB (approx30 keV), a highly obscured and therefore nearly invisible class of AGN, known as Compton thick (CT) AGN, must be assumed to contribute nearly a third of the CXB. In order to constrain the CT fraction of AGNs and the CT number density we consider several hard X-ray AGN luminosity functions and the contribution of blazars to the CXB. Following the unified scheme, the radio AGN luminosity function is relativistically beamed to create a radio blazar luminosity function. An average blazar spectral energy density model is created to transform radio luminosity to X-ray luminosity. We find the blazar contribution to the CXB to be 12% in the 0.5-2 keV band, 7.4% in the 2-10 keV band, 8.9% in the 15-55 keV band, and 100% in the MeV region. When blazars are included in CXB synthesis models, CT AGNs are predicted to be roughly one-third of obscured AGNs, in contrast to the prediction of one half if blazars are not considered. Our model implies a BL Lac X-ray duty cycle ofmore » approx13%, consistent with the concept of intermittent jet activity in low power radio galaxies.« less

Authors:
Publication Date:
OSTI Identifier:
21389301
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 707; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/707/1/778; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMIC PHOTONS; ENERGY BALANCE; ENERGY DENSITY; GALAXY NUCLEI; HARD X RADIATION; KEV RANGE 01-10; LUMINOSITY; MEV RANGE; QUASARS; RADIO GALAXIES; BOSONS; COSMIC RADIATION; COSMIC RADIO SOURCES; ELECTROMAGNETIC RADIATION; ELEMENTARY PARTICLES; ENERGY RANGE; GALAXIES; IONIZING RADIATIONS; KEV RANGE; MASSLESS PARTICLES; OPTICAL PROPERTIES; PHOTONS; PHYSICAL PROPERTIES; RADIATIONS; X RADIATION

Citation Formats

Draper, A R, and Ballantyne, D. R., E-mail: aden.draper@physics.gatech.ed. BALANCING THE COSMIC ENERGY BUDGET: THE COSMIC X-RAY BACKGROUND, BLAZARS, AND THE COMPTON THICK ACTIVE GALACTIC NUCLEUS FRACTION. United States: N. p., 2009. Web. doi:10.1088/0004-637X/707/1/778.
Draper, A R, & Ballantyne, D. R., E-mail: aden.draper@physics.gatech.ed. BALANCING THE COSMIC ENERGY BUDGET: THE COSMIC X-RAY BACKGROUND, BLAZARS, AND THE COMPTON THICK ACTIVE GALACTIC NUCLEUS FRACTION. United States. https://doi.org/10.1088/0004-637X/707/1/778
Draper, A R, and Ballantyne, D. R., E-mail: aden.draper@physics.gatech.ed. 2009. "BALANCING THE COSMIC ENERGY BUDGET: THE COSMIC X-RAY BACKGROUND, BLAZARS, AND THE COMPTON THICK ACTIVE GALACTIC NUCLEUS FRACTION". United States. https://doi.org/10.1088/0004-637X/707/1/778.
@article{osti_21389301,
title = {BALANCING THE COSMIC ENERGY BUDGET: THE COSMIC X-RAY BACKGROUND, BLAZARS, AND THE COMPTON THICK ACTIVE GALACTIC NUCLEUS FRACTION},
author = {Draper, A R and Ballantyne, D. R., E-mail: aden.draper@physics.gatech.ed},
abstractNote = {At energies approx>2 keV, active galactic nuclei (AGNs) are the source of the cosmic X-ray background (CXB). For AGN population synthesis models to replicate the peak region of the CXB (approx30 keV), a highly obscured and therefore nearly invisible class of AGN, known as Compton thick (CT) AGN, must be assumed to contribute nearly a third of the CXB. In order to constrain the CT fraction of AGNs and the CT number density we consider several hard X-ray AGN luminosity functions and the contribution of blazars to the CXB. Following the unified scheme, the radio AGN luminosity function is relativistically beamed to create a radio blazar luminosity function. An average blazar spectral energy density model is created to transform radio luminosity to X-ray luminosity. We find the blazar contribution to the CXB to be 12% in the 0.5-2 keV band, 7.4% in the 2-10 keV band, 8.9% in the 15-55 keV band, and 100% in the MeV region. When blazars are included in CXB synthesis models, CT AGNs are predicted to be roughly one-third of obscured AGNs, in contrast to the prediction of one half if blazars are not considered. Our model implies a BL Lac X-ray duty cycle of approx13%, consistent with the concept of intermittent jet activity in low power radio galaxies.},
doi = {10.1088/0004-637X/707/1/778},
url = {https://www.osti.gov/biblio/21389301}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 707,
place = {United States},
year = {Thu Dec 10 00:00:00 EST 2009},
month = {Thu Dec 10 00:00:00 EST 2009}
}