Insights from LHAASO and IceCube into the origin of the Galactic diffuse TeV--PeV emission

TL;DR

This paper analyzes LHAASO and IceCube data to explore the origin of Galactic diffuse TeV--PeV emission, suggesting pulsar halos significantly contribute to gamma-ray excesses and providing insights into cosmic ray sources.

Contribution

It introduces a model of pulsar halos accounting for diffuse gamma-ray emission, highlighting their role in explaining observed excesses beyond cosmic ray interactions.

Findings

Pulsar halos can explain the gamma-ray excess in the Galactic plane.

Diffuse gamma-ray emission has a significant leptonic component.

Model predictions align with observed gamma-ray profiles.

Abstract

The high-energy diffuse gamma-ray emission and neutrino emission are expected from the Galactic plane, generated by hadronuclear interactions between cosmic rays (CR) and interstellar medium (ISM). Therefore, measurements of these diffuse emissions will provide important clues on the origin and nature of Galactic CRs. Comparing the latest observations of LHAASO and IceCube on the diffuse Galactic gamma-ray and neutrino emissions respectively, we suggest that the diffuse gamma-ray emission at multi-TeV energies contains a considerable contribution of a leptonic component. By modelling the gamma-ray halos powered by middle-aged pulsars in our Galaxy with taking into account the magnetic field configuration and the interstellar radiation field in the Galaxy, we demonstrate that the collective contribution of pulsar halos can account for the excess in the measured diffuse gamma-ray emission with respect to the predicted flux from CR-ISM interactions. The resulting one-dimensional profile along the Galactic longitude is also consistent with the observation.