A New Result on the Origin of the Extragalactic Gamma-ray Background

TL;DR

This study uses image stacking to show that undetected radio sources, including various galaxy types, likely account for over half of the extragalactic gamma-ray background, suggesting a significant contribution from faint sources.

Contribution

The paper introduces a stacking method to estimate the contribution of faint radio sources to the gamma-ray background, highlighting their potential dominance.

Findings

Faint radio sources contribute about 56% of the EGB.

Undetected sources could account for a larger fraction due to sample incompleteness.

Method demonstrates the significance of faint sources in gamma-ray background.

Abstract

In the paper, we continually use the method of image stacking to study the origin of the extragalactic gamma-ray background (EGB) at GeV bands, and find that the Faint Images of the Radio Sky at Twenty centimeters (FIRST) sources undetected by the Large Area Telescope on the Fermi Gamma-ray Space Telescope can contribute about (56{plus minus}6)% of the EGB. Because the FIRST is a flux limited sample of radio sources with incompleteness at the faint limit, we consider that the point-sources, including blazars, non-blazar AGNs,starburst galaxies, could produce a much larger fraction of the EGB.