Detection of a New GeV Source in the Outer Region of the Coma Cluster: A Signature of External Accretion Shock?
The supersonic flow motions associated with infall of baryonic gas toward sheets and filaments, as well as cluster mergers, produces large-scale shock waves. The shocks associated with galaxy clusters can be classified mainly into two categories: internal shocks appearing in the hot intracluster med...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal Letters |
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| Online Access: | https://doi.org/10.3847/2041-8213/ada3d9 |
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| author | Xiao-Bin Chen Kai Wang Yi-Yun Huang Hai-Ming Zhang Shao-Qiang Xi Ruo-Yu Liu Xiang-Yu Wang |
| author_facet | Xiao-Bin Chen Kai Wang Yi-Yun Huang Hai-Ming Zhang Shao-Qiang Xi Ruo-Yu Liu Xiang-Yu Wang |
| author_sort | Xiao-Bin Chen |
| collection | DOAJ |
| description | The supersonic flow motions associated with infall of baryonic gas toward sheets and filaments, as well as cluster mergers, produces large-scale shock waves. The shocks associated with galaxy clusters can be classified mainly into two categories: internal shocks appearing in the hot intracluster medium within the viral radius and external accretion shocks forming in the outer cold region well outside of the virial radius. Cosmic-ray (CR) electrons and/or protons accelerated by these shocks are expected to produce gamma rays through inverse-Compton scattering (ICS) or inelastic pp collisions, respectively. Recent studies have found a spatially extended GeV source within the virial radius, consistent with the internal shock origin. Here, we report the detection of a new GeV source at a distance of about 2 $\mathop{.}\limits^{\unicode{x000b0}}$ 8 from the center of the Coma cluster through the analysis of 16.2 yr of Fermi-LAT data. The hard spectrum of the source, in agreement with the ICS origin, and its location in a large-scale filament of galaxies points to the external accretion shock origin. The gamma-ray (0.1−10 ^3 GeV) luminosity of the source, 1.4 × 10 ^42 erg s ^−1 , suggests that a fraction ~10 ^−3 of the kinetic energy flux through the shock surface is transferred to relativistic CR electrons. |
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| institution | Kabale University |
| issn | 2041-8205 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal Letters |
| spelling | doaj-art-3fb8b0e82b3148c9a7cb93e633db2f492025-01-10T08:07:53ZengIOP PublishingThe Astrophysical Journal Letters2041-82052025-01-019782L4710.3847/2041-8213/ada3d9Detection of a New GeV Source in the Outer Region of the Coma Cluster: A Signature of External Accretion Shock?Xiao-Bin Chen0https://orcid.org/0000-0003-4907-6666Kai Wang1https://orcid.org/0000-0002-5582-8265Yi-Yun Huang2https://orcid.org/0000-0002-6036-985XHai-Ming Zhang3https://orcid.org/0000-0001-6863-5369Shao-Qiang Xi4Ruo-Yu Liu5https://orcid.org/0000-0003-1576-0961Xiang-Yu Wang6https://orcid.org/0000-0002-5881-335XSchool of Astronomy and Space Science, Nanjing University , Nanjing 210023, People’s Republic of China ; xbc@smail.nju.edu.cn, xywang@nju.edu.cn; Key laboratory of Modern Astronomy and Astrophysics (Nanjing University) , Ministry of Education, Nanjing 210023, People’s Republic of ChinaSchool of Astronomy and Space Science, Nanjing University , Nanjing 210023, People’s Republic of China ; xbc@smail.nju.edu.cn, xywang@nju.edu.cn; Key laboratory of Modern Astronomy and Astrophysics (Nanjing University) , Ministry of Education, Nanjing 210023, People’s Republic of ChinaSchool of Astronomy and Space Science, Nanjing University , Nanjing 210023, People’s Republic of China ; xbc@smail.nju.edu.cn, xywang@nju.edu.cn; Key laboratory of Modern Astronomy and Astrophysics (Nanjing University) , Ministry of Education, Nanjing 210023, People’s Republic of ChinaGuangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University , Nanning 530004, People’s Republic of ChinaKey Laboratory of Particle Astrophysics & Experimental Physics Division & Computing Center , Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing, People’s Republic of ChinaSchool of Astronomy and Space Science, Nanjing University , Nanjing 210023, People’s Republic of China ; xbc@smail.nju.edu.cn, xywang@nju.edu.cn; Key laboratory of Modern Astronomy and Astrophysics (Nanjing University) , Ministry of Education, Nanjing 210023, People’s Republic of ChinaSchool of Astronomy and Space Science, Nanjing University , Nanjing 210023, People’s Republic of China ; xbc@smail.nju.edu.cn, xywang@nju.edu.cn; Key laboratory of Modern Astronomy and Astrophysics (Nanjing University) , Ministry of Education, Nanjing 210023, People’s Republic of ChinaThe supersonic flow motions associated with infall of baryonic gas toward sheets and filaments, as well as cluster mergers, produces large-scale shock waves. The shocks associated with galaxy clusters can be classified mainly into two categories: internal shocks appearing in the hot intracluster medium within the viral radius and external accretion shocks forming in the outer cold region well outside of the virial radius. Cosmic-ray (CR) electrons and/or protons accelerated by these shocks are expected to produce gamma rays through inverse-Compton scattering (ICS) or inelastic pp collisions, respectively. Recent studies have found a spatially extended GeV source within the virial radius, consistent with the internal shock origin. Here, we report the detection of a new GeV source at a distance of about 2 $\mathop{.}\limits^{\unicode{x000b0}}$ 8 from the center of the Coma cluster through the analysis of 16.2 yr of Fermi-LAT data. The hard spectrum of the source, in agreement with the ICS origin, and its location in a large-scale filament of galaxies points to the external accretion shock origin. The gamma-ray (0.1−10 ^3 GeV) luminosity of the source, 1.4 × 10 ^42 erg s ^−1 , suggests that a fraction ~10 ^−3 of the kinetic energy flux through the shock surface is transferred to relativistic CR electrons.https://doi.org/10.3847/2041-8213/ada3d9Galaxy clustersShocksCosmic rays |
| spellingShingle | Xiao-Bin Chen Kai Wang Yi-Yun Huang Hai-Ming Zhang Shao-Qiang Xi Ruo-Yu Liu Xiang-Yu Wang Detection of a New GeV Source in the Outer Region of the Coma Cluster: A Signature of External Accretion Shock? The Astrophysical Journal Letters Galaxy clusters Shocks Cosmic rays |
| title | Detection of a New GeV Source in the Outer Region of the Coma Cluster: A Signature of External Accretion Shock? |
| title_full | Detection of a New GeV Source in the Outer Region of the Coma Cluster: A Signature of External Accretion Shock? |
| title_fullStr | Detection of a New GeV Source in the Outer Region of the Coma Cluster: A Signature of External Accretion Shock? |
| title_full_unstemmed | Detection of a New GeV Source in the Outer Region of the Coma Cluster: A Signature of External Accretion Shock? |
| title_short | Detection of a New GeV Source in the Outer Region of the Coma Cluster: A Signature of External Accretion Shock? |
| title_sort | detection of a new gev source in the outer region of the coma cluster a signature of external accretion shock |
| topic | Galaxy clusters Shocks Cosmic rays |
| url | https://doi.org/10.3847/2041-8213/ada3d9 |
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