Decisive evidence for a global cosmic-ray feature in gamma-ray data
Abstract
We analyze 17 years of Fermi-LAT data to study the diffuse γ-ray emission along the Galactic plane and its connection to cosmic-ray (CR) propagation. Accounting for correlated instrumental systematics, we find decisive evidence for a spectral break at ∼20−30 GeV, present across the inner Galactic disk, with a preference of Δχ2=39.78 ($4.44 σ$ global). The energy and amplitude of this feature are in striking agreement with the spectral feature observed in local CR nuclei, indicating that it is a global property of the Galactic disk rather than a local phenomenon. The measured slope change, Δγ≃ 0.20, is consistent with local CR data and with expectations from a transition in the CR diffusion regime from Kolmogorov to Kraichnan turbulence. Our results provide strong evidence that diffuse γ-ray emission along the Galactic disk is dominated by π0−decay emission up to a hundred GeV. These findings provide key insights into the origin of the CR spectral hardening and the propagation of CRs throughout the Galaxy, and illustrate how this multimessenger approach can be used to probe the origin of features in the CR spectra, such as the long-studied CR Knee.
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BibTeX
@misc{valenciano2026decisive,
title = {{Decisive evidence for a global cosmic-ray feature in gamma-ray data}},
author = {Fernando Valenciano and Pedro De la Torre Luque and Daniele Gaggero and Jorge Martin Camalich},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.28757},
eprint = {2608.28757},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.28757},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Decisive evidence for a global cosmic-ray feature in gamma-ray data
AU - Fernando Valenciano
AU - Pedro De la Torre Luque
AU - Daniele Gaggero
AU - Jorge Martin Camalich
PY - 2026
DA - 2026/08/28
PB - arXiv
DO - 10.48550/arxiv.2608.28757
UR - https://arxiv.org/abs/2608.28757
AB - We analyze 17 years of Fermi-LAT data to study the diffuse γ-ray emission along the Galactic plane and its connection to cosmic-ray (CR) propagation. Accounting for correlated instrumental systematics, we find decisive evidence for a spectral break at ∼20−30 GeV, present across the inner Galactic disk, with a preference of Δχ^2=39.78 ($4.44 σ$ global). The energy and amplitude of this feature are in striking agreement with the spectral feature observed in local CR nuclei, indicating that it is a global property of the Galactic disk rather than a local phenomenon. The measured slope change, Δγ≃ 0.20, is consistent with local CR data and with expectations from a transition in the CR diffusion regime from Kolmogorov to Kraichnan turbulence. Our results provide strong evidence that diffuse γ-ray emission along the Galactic disk is dominated by π^0−decay emission up to a hundred GeV. These findings provide key insights into the origin of the CR spectral hardening and the propagation of CRs throughout the Galaxy, and illustrate how this multimessenger approach can be used to probe the origin of features in the CR spectra, such as the long-studied CR Knee.
ER -