BALANCING THE COSMIC ENERGY BUDGET: THE COSMIC X-RAY BACKGROUND, BLAZARS, AND THE COMPTON THICK ACTIVE GALACTIC NUCLEUS FRACTION
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.
- OSTI ID:
- 21389301
- Journal Information:
- Astrophysical Journal, Vol. 707, Issue 1; Other Information: DOI: 10.1088/0004-637X/707/1/778; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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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
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X RADIATION