A Possible Common Physics Picture Reflected by the Gamma-Ray Emission of the Galactic Center
Long-term observations of the Galactic center by Fermi and HESS have revealed a novel phenomenon: the high-energy gamma-ray spectrum from the gamma-ray source HESS J1745-290 exhibits a double power-law structure. In this study, we propose a new explanation for this phenomenon. We suggest that the lo...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ade3ce |
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| author | Lin Nie Yi-Qing Guo Si-Ming Liu |
| author_facet | Lin Nie Yi-Qing Guo Si-Ming Liu |
| author_sort | Lin Nie |
| collection | DOAJ |
| description | Long-term observations of the Galactic center by Fermi and HESS have revealed a novel phenomenon: the high-energy gamma-ray spectrum from the gamma-ray source HESS J1745-290 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 anticipate that this double power-law structure may be widely present in the halo of a Galactic cosmic-ray source or a slow-diffusion region. We hope that future observations will detect more such sources, allowing us to further test and validate our model. |
| format | Article |
| id | doaj-art-d26ca5ac5336430f98935f67ed858d1f |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-d26ca5ac5336430f98935f67ed858d1f2025-08-20T03:11:55ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198819310.3847/1538-4357/ade3ceA Possible Common Physics Picture Reflected by the Gamma-Ray Emission of the Galactic CenterLin Nie0https://orcid.org/0000-0003-0969-5446Yi-Qing Guo1https://orcid.org/0000-0003-4932-9619Si-Ming Liu2https://orcid.org/0000-0003-1039-9521School of Physical Science and Technology, Southwest Jiaotong University , Chengdu, 610031, People’s Republic of China ; liusm@swjtu.edu.cn; Key Laboratory of Particle Astrophysics, Institute of High Energy Physics , Chinese Academy of Sciences, Beijing, 100049, People’s Republic of China ; guoyq@ihep.ac.cnKey Laboratory of Particle Astrophysics, Institute of High Energy Physics , Chinese Academy of Sciences, Beijing, 100049, People’s Republic of China ; guoyq@ihep.ac.cn; University of Chinese Academy of Sciences , Beijing 100049, People’s Republic of China; TIANFU Cosmic Ray Research Center , Chengdu 610000, People’s Republic of ChinaSchool of Physical Science and Technology, Southwest Jiaotong University , Chengdu, 610031, People’s Republic of China ; liusm@swjtu.edu.cnLong-term observations of the Galactic center by Fermi and HESS have revealed a novel phenomenon: the high-energy gamma-ray spectrum from the gamma-ray source HESS J1745-290 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 anticipate that this double power-law structure may be widely present in the halo of a Galactic cosmic-ray source or a slow-diffusion region. We hope that future observations will detect more such sources, allowing us to further test and validate our model.https://doi.org/10.3847/1538-4357/ade3ceGalactic cosmic raysDiffuse radiationGalactic center |
| spellingShingle | Lin Nie Yi-Qing Guo Si-Ming Liu A Possible Common Physics Picture Reflected by the Gamma-Ray Emission of the Galactic Center The Astrophysical Journal Galactic cosmic rays Diffuse radiation Galactic center |
| title | A Possible Common Physics Picture Reflected by the Gamma-Ray Emission of the Galactic Center |
| title_full | A Possible Common Physics Picture Reflected by the Gamma-Ray Emission of the Galactic Center |
| title_fullStr | A Possible Common Physics Picture Reflected by the Gamma-Ray Emission of the Galactic Center |
| title_full_unstemmed | A Possible Common Physics Picture Reflected by the Gamma-Ray Emission of the Galactic Center |
| title_short | A Possible Common Physics Picture Reflected by the Gamma-Ray Emission of the Galactic Center |
| title_sort | possible common physics picture reflected by the gamma ray emission of the galactic center |
| topic | Galactic cosmic rays Diffuse radiation Galactic center |
| url | https://doi.org/10.3847/1538-4357/ade3ce |
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