The Contribution of Blazars to the Extragalactic Diffuse Gamma-ray Background and Their Future Spatial Resolution

TL;DR

This study models blazar evolution to explain the diffuse gamma-ray background observed by Fermi-LAT, predicting most blazar flux will be resolved into point sources within five years, impacting dark matter detection efforts.

Contribution

It introduces a simple, three-parameter blazar evolution model that aligns with Fermi-LAT observations and predicts significant source resolution in future observations.

Findings

Blazars can account for the entire DGRB spectrum.

Over 95% of blazar flux will be resolved into point sources within 5 years.

The model constrains the contribution of blazars to the gamma-ray background.

Abstract

We examine the constraints on the luminosity-dependent density evolution model for the evolution of blazars given the observed spectrum of the diffuse gamma-ray background (DGRB), blazar source-count distribution, and the blazar spectral energy distribution sequence model, which relates the observed the blazar spectrum to its luminosity. We show that the DGRB observed by the Large Area Telescope (LAT) aboard the Fermi Gamma Ray Space Telescope can be produced entirely by gamma-ray emission from blazars and nonblazar active galactic nuclei, and that our blazar evolution model is consistent with and constrained by the spectrum of the DGRB and flux source-count distribution function of blazars observed by Fermi-LAT. Our results are consistent with previous work that used EGRET spectral data to forecast the Fermi-LAT DGRB. The model includes only three free parameters, and forecasts that >~ 95% of the flux from blazars will be resolved into point sources by Fermi-LAT with 5 years of observation, with a corresponding reduction of the flux in the DGRB by a factor of ~2 to 3 (95% confidence level), which has implications for the Fermi-LAT's sensitivity to dark matter annihilation photons.