Resolved and unresolved Galactic gamma-ray sources

TL;DR

This paper analyzes the Galactic gamma-ray flux, distinguishing between resolved sources, unresolved sources, and interstellar emission, using data from HAWC and LHAASO to estimate their contributions.

Contribution

It introduces a method to estimate the total luminosity of Galactic gamma-ray sources and quantify the unresolved sources' contribution using catalog distributions.

Findings

Unresolved sources contribute significantly to the gamma-ray flux.

Interstellar emission dominates the diffuse gamma-ray flux.

Unresolved sources are measurable but less dominant than interstellar emission.

Abstract

The Galactic gamma-ray flux can be described as the sum of two components: the first is due to the emission from an ensemble of discrete sources, and the second is formed by the photons produced by cosmic rays propagating in interstellar space and interacting with gas or radiation fields. The source component is partially resolved as the contributions from individual sources, but a fraction is unresolved and appears as a diffuse flux. Both the unresolved source flux and the interstellar emission flux encode information of great significance for high energy astrophysics, and therefore the separation of these two contributions is very important. In this work we use the distributions in celestial coordinates of the objects contained in the catalogs obtained by the Extensive Air Showers telescopes HAWC and LHAASO to estimate the total luminosity of the Galactic gamma--ray sources and the contribution of unresolved sources to the diffuse gamma--ray flux. This analysis suggests that while the flux from unresolved sources is measurable and important, the dominant contribution to the diffuse flux over most of the celestial sphere is interstellar emission.