TeV-PeV Gamma-ray and Neutrino Emission in the Galactic Plane

Abstract

We model the LHAASO observation of diffuse TeV--PeV $\gamma$ rays in the Galactic plane as the sum of unresolved leptonic emission from pulsar wind nebulae and hadronic emission from supernova-injected cosmic-ray (CR) protons. We investigate uncertainties in the radial distribution of the infrared component of the interstellar radiation field (ISRF), using profiles with enhanced photon densities in the inner Galaxy. We quantify their effects on $\gamma \gamma$ attenuation of the diffuse $\gamma$-ray emission. The alternative ISRF models affect the LHAASO diffuse fit only modestly, as the analysis excludes the Galactic center direction and applies source masks in the Galactic plane. Using the hadronic normalization inferred from the LHAASO fit for various ISRF models, the associated $pp$ neutrino emission remains consistent with the IceCube all-sky measurement, while the flux from the Galactic Ridge region remains compatible with current ANTARES and KM3NeT constraints. Since the modified infrared profiles differ most strongly toward the inner Galaxy, we also examine their impact on inverse-Compton emission from point sources near the central molecular zone. These same models can noticeably modify the hadronic and inverse-Compton $\gamma$-ray emission above $\sim 10$ TeV from sources in the central region. Future KM3NeT observations, combined with $\gamma$-ray measurements of individual sources, can probe the inner-Galaxy CR population and constrain the radial distribution of the ISRF near the Galactic Center.

11 pages, 7 figures, accepted for publication in ApJL

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