Balancing the Cosmic Energy Budget: The Cosmic X-ray Background, Blazars
  and the Compton Thick AGN Fraction
  At energies ~>2 keV, active galactic nuclei (AGN) are the source of the
cosmic X-ray background (CXB). For AGN population synthesis models to replicate
the peak region of the CXB (~30 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
AGN 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 AGN are predicted to be
roughly one-third of obscured AGN, in contrast to the prediction of one half if
blazars are not considered. Our model implies a BL Lac X-ray duty cycle of
~13%, consistent with the concept of intermittent jet activity in low power
radio galaxies.
