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

Journal Article · Thu Dec 10 04:00:00 EST 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/707/1/778· OSTI ID:21389301

Draper, A R

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, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 707; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BOSONS
COSMIC PHOTONS
COSMIC RADIATION
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ENERGY BALANCE
ENERGY DENSITY
ENERGY RANGE
GALAXIES
GALAXY NUCLEI
HARD X RADIATION
IONIZING RADIATIONS
KEV RANGE
KEV RANGE 01-10
LUMINOSITY
MASSLESS PARTICLES
MEV RANGE
OPTICAL PROPERTIES
PHOTONS
PHYSICAL PROPERTIES
QUASARS
RADIATIONS
RADIO GALAXIES
X RADIATION