A Possible Common Physic Picture Reflected by the Gamma Ray Emission of the Galactic Center

Lin Nie; Yi-Qing Guo; Si-Ming Liu

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arXiv · 2503.05261

A Possible Common Physic Picture Reflected by the Gamma Ray Emission of the Galactic Center

Lin Nie·Yi-Qing Guo·Si-Ming Liu

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Abstract

Long-term observations of the Galactic center by Fermi and HESS have revealed a novel phenomenon: the high-energy gamma-ray spectrum from the Galactic center exhibits a double power-law structure. In this study, we propose a new explanation for this phenomenon. We suggest that the low-energy (GeV) power-law spectrum originates from interactions between trapped background ``sea" cosmic ray particles and the dense gaseous environment near the Galactic center. In contrast, the bubble-like structure in the high-energy (TeV) spectrum is produced by protons accelerated during active phases of the Galactic center, through the same physical process. Based on this framework, we first calculate the gamma-ray emission generated by cosmic ray protons accelerated in the Galactic center. Then, using a spatially-dependent cosmic ray propagation model, we compute the energy spectrum of background ``sea" cosmic ray protons and their associated diffuse gamma-ray emission in the Galactic center region. The results closely reproduce the observations from Fermi-LAT and HESS, suggesting that their long-term data support this picture: high-energy cosmic rays in the local region originate from nearby cosmic ray sources, while low-energy cosmic rays are a unified contribution from distant cosmic ray sources. We predict that some extended Galactic sources, which remain undetectable in the GeV energy range, may become observable in the TeV range. We hope that future observations will detect more such sources, allowing us to further test and validate our model.

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Lin Nie, Yi-Qing Guo, Si-Ming Liu. 2025-03-07. A Possible Common Physic Picture Reflected by the Gamma Ray Emission of the Galactic Center. https://arxiv.org/abs/2503.05261

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