A New Perspective on the Diffuse Gamma-Ray Emission Excess

TL;DR

This paper proposes that the diffuse gamma-ray emission excess observed by LHAASO can be explained by signal leakage from known pulsar wind nebulae and unresolved sources, using a two-zone diffusion model for electrons.

Contribution

It introduces a new perspective that the DGE excess is due to incomplete masking of extended PWNe/halos signals, modeled through a two-zone diffusion approach.

Findings

The DGE excess can be explained by signal leakage from known sources.

A two-zone diffusion model fits the observed excess.

Unresolved sources also contribute to the excess.

Abstract

The Large High-Altitude Air Shower Observatory (LHAASO) recently published measurements of diffuse Galactic gamma-ray emission (DGE) in the 10-1000 TeV energy range. The measured DGE flux is significantly higher than the expectation from hadronic interactions between cosmic rays (CRs) and the interstellar medium. This excess has been proposed to originate from unknown extended sources produced by electron radiation, such as pulsar wind nebulae or pulsar halos (PWNe/halos). In this study, we propose a new perspective to explain the DGE excess observed by LHAASO. The masking regions used in the LHAASO DGE measurement may not fully encompass the extended signals of PWNe/halos. By employing a two-zone diffusion model for electrons around pulsars, we find that the DGE excess in most regions of the Galactic plane can be well explained by the signal leakage model under certain parameters. Our results indicate that the signal leakage from known sources and contributions from unresolved sources should be considered complementary in explaining the DGE excess.