The Blazar Share of the Diffuse Background as a Function of Energy: A Two-Spectrum Consistency Test

Blazars are the largest identified contributor to the isotropic diffuse gamma-ray background, and their share is strongly energy dependent. Fixing the blazar component to supply the published fraction above 10 GeV and giving it the harder spectrum reported for the unresolved blazar population, this paper computes the blazar fraction at energies from 0.1 to 300 GeV and the fraction integrated over the full band. It finds fraction at 1GeV = 0.518; fraction at 100GeV = 1.43; integrated fraction above 100MeV = 0.374. The integrated fraction is far below the high-energy fraction, so statements that blazars explain the background and statements that they explain only part of it can both be true, at different energies. The study is simulated and computed from published values, not measured.