A simplified view of blazars: contribution to the X-ray and gamma-ray cosmic backgrounds

TL;DR

This paper extends the 'blazar simplified view' to predict blazar contributions to X-ray and gamma-ray backgrounds, showing they can account for most of the high-energy cosmic backgrounds and challenging the 'blazar sequence' model.

Contribution

It provides new estimates of blazar contributions to cosmic backgrounds across a wide energy range, based on the simplified view paradigm.

Findings

Blazars can explain up to 100% of the gamma-ray background above 10 GeV.

Blazars contribute about 4-5% to the X-ray background between 1-50 keV.

The 'blazar sequence' model is inconsistent with observed gamma-ray background levels.

Abstract

The "blazar simplified view" is a new paradigm that explains well the diverse statistical properties of blazars observed over the entire electromagnetic spectrum on the basis of minimal assumptions on blazars' physical and geometrical properties. In this paper, the fourth in a series, we extend the predictions of this paradigm below the sensitivity of existing surveys and estimate the contribution of blazars to the X-ray and gamma-ray extragalactic backgrounds. We find that the integrated light from blazars can explain up to 100% of the cosmic background at energies larger than ~10 GeV, and contribute ~40 to 70% of the gamma-ray diffuse radiation between 100 MeV and 10 GeV. The contribution of blazars to the X-ray background, between 1 and 50 keV, is approximately constant and of the order of 4-5%. On the basis of an interpolation between the estimated flux at X-ray and gamma-ray energies we can expect that the contribution of blazars raises to ~10% at 100 keV, and continues to increase with energy until it becomes the dominant component at a few MeV. Finally, we show that a strong dependence of the synchrotron peak frequency on luminosity, as postulated by the "blazar sequence", is ruled out by the observational data as it predicts a gamma-ray background above a few GeV that is far in excess of the observed value.