A new model for the Fermi-LAT Extragalactic Gamma-Ray Background

TL;DR

This paper models the contribution of blazars to the Fermi-LAT gamma-ray background, finding they account for 45% overall but cannot explain the entire spectrum, especially at low and high energies, suggesting other sources are involved.

Contribution

It introduces a new model linking blazar gamma-ray emission to radio galaxy luminosity functions and the blazar sequence, providing a comprehensive contribution estimate.

Findings

Blazars contribute 45% to the gamma-ray background.

Star-forming galaxies explain low-energy background.

An unknown component is needed at high energies.

Abstract

We compute the contribution of blazars (Flat Spectrum Radio Quasars and BL-Lacs) to the Fermi-LAT Extragalactic gamma-ray Background, assuming a gamma-ray luminosity function proportional to the luminosity function of radio galaxies and the Spectral Energy Distribution of blazars given by the so-called blazar sequence. We find that blazars account for the 45% of the total Fermi-LAT EGB. However, at low (<10 GeV) and high (>50 GeV) energies the blazar contribution falls short to account for the observed background light. At E<10 GeV, the Extragalactic gamma-ray Background can be fully explained by considering the additional contribution of star-forming galaxies, whereas at very high energies, where the absorption due to Extragalactic Background Light dominates, the observed background calls for an additional unknown component.