Measurement of Ultra-High-Energy Diffuse Gamma-Ray Emission of the Galactic Plane from 10 TeV to 1 PeV with LHAASO-KM2A

Zhen Cao^{1

2

3}, F Aharonian^{4

5}, Q An^{6

7}, Axikegu⁸, Y X Bai^{1

3}, Y W Bao⁹, D Bastieri¹⁰, X J Bi^{1

2

3}, Y J Bi^{1

3}, J T Cai¹⁰, Q Cao¹¹, W Y Cao⁷, Zhe Cao^{6

7}, J Chang¹², J F Chang^{1

3

6}, A M Chen¹³, E S Chen^{1

2

3}, Liang Chen¹⁴, Lin Chen⁸, Long Chen⁸, M J Chen^{1

3}, M L Chen^{1

3

6}, Q H Chen⁸, S H Chen^{1

2

3}, S Z Chen^{1

3}, T L Chen¹⁵, Y Chen⁹, N Cheng^{1

3}, Y D Cheng^{1

3}, M Y Cui¹², S W Cui¹¹, X H Cui¹⁶, Y D Cui¹⁷, B Z Dai¹⁸, H L Dai^{1

3

6}, Z G Dai⁷, Danzengluobu¹⁵, D Della Volpe¹⁹, X Q Dong^{1

2

3}, K K Duan¹², J H Fan¹⁰, Y Z Fan¹², J Fang¹⁸, K Fang^{1

3}, C F Feng²⁰, L Feng¹², S H Feng^{1

3}, X T Feng²⁰, Y L Feng¹⁵, S Gabici²¹, B Gao^{1

3}, C D Gao²⁰, L Q Gao^{1

2

3}, Q Gao¹⁵, W Gao^{1

3}, W K Gao^{1

2

3}, M M Ge¹⁸, L S Geng^{1

3}, G Giacinti¹³, G H Gong²², Q B Gou^{1

3}, M H Gu^{1

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6}, F L Guo¹⁴, X L Guo⁸, Y Q Guo^{1

3}, Y Y Guo¹², Y A Han²³, H H He^{1

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3}, H N He¹², J Y He¹², X B He¹⁷, Y He⁸, M Heller¹⁹, Y K Hor¹⁷, B W Hou^{1

2

3}, C Hou^{1

3}, X Hou²⁴, H B Hu^{1

2

3}, Q Hu^{7

12}, S C Hu^{1

2

3}, D H Huang⁸, T Q Huang^{1

3}, W J Huang¹⁷, X T Huang²⁰, X Y Huang¹², Y Huang^{1

2

3}, Z C Huang⁸, X L Ji^{1

3

6}, H Y Jia⁸, K Jia²⁰, K Jiang^{6

7}, X W Jiang^{1

3}, Z J Jiang¹⁸, M Jin⁸, M M Kang²⁵, T Ke^{1

3}, D Kuleshov²⁶, K Kurinov²⁶, B B Li¹¹, Cheng Li^{6

7}, Cong Li^{1

3}, D Li^{1

2

3}, F Li^{1

3

6}, H B Li^{1

3}, H C Li^{1

3}, H Y Li^{7

12}, J Li^{7

12}, Jian Li⁷, Jie Li^{1

3

6}, K Li^{1

3}, W L Li²⁰, W L Li¹³, X R Li^{1

3}, Xin Li^{6

7}, Y Z Li^{1

2

3}, Zhe Li^{1

3}, Zhuo Li²⁷, E W Liang²⁸, Y F Liang²⁸, S J Lin¹⁷, B Liu⁷, C Liu^{1

3}, D Liu²⁰, H Liu⁸, H D Liu²³, J Liu^{1

3}, J L Liu^{1

3}, J Y Liu^{1

3}, M Y Liu¹⁵, R Y Liu⁹, S M Liu⁸, W Liu^{1

3}, Y Liu¹⁰, Y N Liu²², R Lu¹⁸, Q Luo¹⁷, H K Lv^{1

3}, B Q Ma²⁷, L L Ma^{1

3}, X H Ma^{1

3}, J R Mao²⁴, Z Min^{1

3}, W Mitthumsiri²⁹, H J Mu²³, Y C Nan^{1

3}, A Neronov²¹, Z W Ou¹⁷, B Y Pang⁸, P Pattarakijwanich²⁹, Z Y Pei¹⁰, M Y Qi^{1

3}, Y Q Qi¹¹, B Q Qiao^{1

3}, J J Qin⁷, D Ruffolo²⁹, A Sáiz²⁹, D Semikoz²¹, C Y Shao¹⁷, L Shao¹¹, O Shchegolev^{26

30}, X D Sheng^{1

3}, F W Shu³¹, H C Song²⁷, Yu V Stenkin^{26

30}, V Stepanov²⁶, Y Su¹², Q N Sun⁸, X N Sun²⁸, Z B Sun³², P H T Tam¹⁷, Q W Tang³¹, Z B Tang^{6

7}, W W Tian^{2

16}, C Wang³², C B Wang⁸, G W Wang⁷, H G Wang¹⁰, H H Wang¹⁷, J C Wang²⁴, K Wang⁹, L P Wang²⁰, L Y Wang^{1

3}, P H Wang⁸, R Wang²⁰, W Wang¹⁷, X G Wang²⁸, X Y Wang⁹, Y Wang⁸, Y D Wang^{1

3}, Y J Wang^{1

3}, Z H Wang²⁵, Z X Wang¹⁸, Zhen Wang¹³, Zheng Wang^{1

3

6}, D M Wei¹², J J Wei¹², Y J Wei^{1

2

3}, T Wen¹⁸, C Y Wu^{1

3}, H R Wu^{1

3}, S Wu^{1

3}, X F Wu¹², Y S Wu⁷, S Q Xi^{1

3}, J Xia^{7

12}, J J Xia⁸, G M Xiang^{2

14}, D X Xiao¹¹, G Xiao^{1

3}, G G Xin^{1

3}, Y L Xin⁸, Y Xing¹⁴, Z Xiong^{1

2

3}, D L Xu¹³, R F Xu^{1

2

3}, R X Xu²⁷, W L Xu²⁵, L Xue²⁰, D H Yan¹⁸, J Z Yan¹², T Yan^{1

3}, C W Yang²⁵, F Yang¹¹, F F Yang^{1

3

6}, H W Yang¹⁷, J Y Yang¹⁷, L L Yang¹⁷, M J Yang^{1

3}, R Z Yang⁷, S B Yang¹⁸, Y H Yao²⁵, Z G Yao^{1

3}, Y M Ye²², L Q Yin^{1

3}, N Yin²⁰, X H You^{1

3}, Z Y You^{1

2

3}, Y H Yu⁷, Q Yuan¹², H Yue^{1

2

3}, H D Zeng¹², T X Zeng^{1

3

6}, W Zeng¹⁸, M Zha^{1

3}, B B Zhang⁹, F Zhang⁸, H M Zhang⁹, H Y Zhang^{1

3}, J L Zhang¹⁶, L X Zhang¹⁰, Li Zhang¹⁸, P F Zhang¹⁸, P P Zhang^{7

12}, R Zhang^{7

12}, S B Zhang^{2

16}, S R Zhang¹¹, S S Zhang^{1

3}, X Zhang⁹, X P Zhang^{1

3}, Y F Zhang⁸, Yi Zhang^{1

12}, Yong Zhang^{1

3}, B Zhao⁸, J Zhao^{1

3}, L Zhao^{6

7}, L Z Zhao¹¹, S P Zhao^{12

20}, F Zheng³², B Zhou^{1

3}, H Zhou¹³, J N Zhou¹⁴, M Zhou³¹, P Zhou⁹, R Zhou²⁵, X X Zhou⁸, C G Zhu²⁰, F R Zhu⁸, H Zhu¹⁶, K J Zhu^{1

2

3

6}, X Zuo^{1

3}; LHAASO Collaboration

Affiliations

¹ Key Laboratory of Particle Astrophyics & Experimental Physics Division & Computing Center, Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing, China.
² University of Chinese Academy of Sciences, 100049 Beijing, China.
³ Tianfu Cosmic Ray Research Center, 610000 Chengdu, Sichuan, China.
⁴ Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, 2 Dublin, Ireland.
⁵ Max-Planck-Institut for Nuclear Physics, P.O. Box 103980, 69029 Heidelberg, Germany.
⁶ State Key Laboratory of Particle Detection and Electronics, 230026 Hefei, China.
⁷ University of Science and Technology of China, 230026 Hefei, Anhui, China.
⁸ School of Physical Science and Technology & School of Information Science and Technology, Southwest Jiaotong University, 610031 Chengdu, Sichuan, China.
⁹ School of Astronomy and Space Science, Nanjing University, 210023 Nanjing, Jiangsu, China.
¹⁰ Center for Astrophysics, Guangzhou University, 510006 Guangzhou, Guangdong, China.
¹¹ Hebei Normal University, 050024 Shijiazhuang, Hebei, China.
¹² Key Laboratory of Dark Matter and Space Astronomy & Key Laboratory of Radio Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, 210023 Nanjing, Jiangsu, China.
¹³ Tsung-Dao Lee Institute & School of Physics and Astronomy, Shanghai Jiao Tong University, 200240 Shanghai, China.
¹⁴ Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 200030 Shanghai, China.
¹⁵ Key Laboratory of Cosmic Rays (Tibet University), Ministry of Education, 850000 Lhasa, Tibet, China.
¹⁶ National Astronomical Observatories, Chinese Academy of Sciences, 100101 Beijing, China.
¹⁷ School of Physics and Astronomy (Zhuhai) & School of Physics (Guangzhou) & Sino-French Institute of Nuclear Engineering and Technology (Zhuhai), Sun Yat-sen University, 519000 Zhuhai & 510275 Guangzhou, Guangdong, China.
¹⁸ School of Physics and Astronomy, Yunnan University, 650091 Kunming, Yunnan, China.
¹⁹ Département de Physique Nucléaire et Corpusculaire, Faculté de Sciences, Université de Genève, 24 Quai Ernest Ansermet, 1211 Geneva, Switzerland.
²⁰ Institute of Frontier and Interdisciplinary Science, Shandong University, 266237 Qingdao, Shandong, China.
²¹ APC, Université Paris Cité, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, 119 75205 Paris, France.
²² Department of Engineering Physics, Tsinghua University, 100084 Beijing, China.
²³ School of Physics and Microelectronics, Zhengzhou University, 450001 Zhengzhou, Henan, China.
²⁴ Yunnan Observatories, Chinese Academy of Sciences, 650216 Kunming, Yunnan, China.
²⁵ College of Physics, Sichuan University, 610065 Chengdu, Sichuan, China.
²⁶ Institute for Nuclear Research of Russian Academy of Sciences, 117312 Moscow, Russia.
²⁷ School of Physics, Peking University, 100871 Beijing, China.
²⁸ School of Physical Science and Technology, Guangxi University, 530004 Nanning, Guangxi, China.
²⁹ Department of Physics, Faculty of Science, Mahidol University, 10400 Bangkok, Thailand.
³⁰ Moscow Institute of Physics and Technology, 141700 Moscow, Russia.
³¹ Center for Relativistic Astrophysics and High Energy Physics, School of Physics and Materials Science & Institute of Space Science and Technology, Nanchang University, 330031 Nanchang, Jiangxi, China.
³² National Space Science Center, Chinese Academy of Sciences, 100190 Beijing, China.

PMID: 37897763
DOI: 10.1103/PhysRevLett.131.151001

Measurement of Ultra-High-Energy Diffuse Gamma-Ray Emission of the Galactic Plane from 10 TeV to 1 PeV with LHAASO-KM2A

Zhen Cao et al. Phys Rev Lett. 2023.

. 2023 Oct 13;131(15):151001.

doi: 10.1103/PhysRevLett.131.151001.

Authors

Affiliations

¹ Key Laboratory of Particle Astrophyics & Experimental Physics Division & Computing Center, Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing, China.
² University of Chinese Academy of Sciences, 100049 Beijing, China.
³ Tianfu Cosmic Ray Research Center, 610000 Chengdu, Sichuan, China.
⁴ Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, 2 Dublin, Ireland.
⁵ Max-Planck-Institut for Nuclear Physics, P.O. Box 103980, 69029 Heidelberg, Germany.
⁶ State Key Laboratory of Particle Detection and Electronics, 230026 Hefei, China.
⁷ University of Science and Technology of China, 230026 Hefei, Anhui, China.
⁸ School of Physical Science and Technology & School of Information Science and Technology, Southwest Jiaotong University, 610031 Chengdu, Sichuan, China.
⁹ School of Astronomy and Space Science, Nanjing University, 210023 Nanjing, Jiangsu, China.
¹⁰ Center for Astrophysics, Guangzhou University, 510006 Guangzhou, Guangdong, China.
¹¹ Hebei Normal University, 050024 Shijiazhuang, Hebei, China.
¹² Key Laboratory of Dark Matter and Space Astronomy & Key Laboratory of Radio Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, 210023 Nanjing, Jiangsu, China.
¹³ Tsung-Dao Lee Institute & School of Physics and Astronomy, Shanghai Jiao Tong University, 200240 Shanghai, China.
¹⁴ Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 200030 Shanghai, China.
¹⁵ Key Laboratory of Cosmic Rays (Tibet University), Ministry of Education, 850000 Lhasa, Tibet, China.
¹⁶ National Astronomical Observatories, Chinese Academy of Sciences, 100101 Beijing, China.
¹⁷ School of Physics and Astronomy (Zhuhai) & School of Physics (Guangzhou) & Sino-French Institute of Nuclear Engineering and Technology (Zhuhai), Sun Yat-sen University, 519000 Zhuhai & 510275 Guangzhou, Guangdong, China.
¹⁸ School of Physics and Astronomy, Yunnan University, 650091 Kunming, Yunnan, China.
¹⁹ Département de Physique Nucléaire et Corpusculaire, Faculté de Sciences, Université de Genève, 24 Quai Ernest Ansermet, 1211 Geneva, Switzerland.
²⁰ Institute of Frontier and Interdisciplinary Science, Shandong University, 266237 Qingdao, Shandong, China.
²¹ APC, Université Paris Cité, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, 119 75205 Paris, France.
²² Department of Engineering Physics, Tsinghua University, 100084 Beijing, China.
²³ School of Physics and Microelectronics, Zhengzhou University, 450001 Zhengzhou, Henan, China.
²⁴ Yunnan Observatories, Chinese Academy of Sciences, 650216 Kunming, Yunnan, China.
²⁵ College of Physics, Sichuan University, 610065 Chengdu, Sichuan, China.
²⁶ Institute for Nuclear Research of Russian Academy of Sciences, 117312 Moscow, Russia.
²⁷ School of Physics, Peking University, 100871 Beijing, China.
²⁸ School of Physical Science and Technology, Guangxi University, 530004 Nanning, Guangxi, China.
²⁹ Department of Physics, Faculty of Science, Mahidol University, 10400 Bangkok, Thailand.
³⁰ Moscow Institute of Physics and Technology, 141700 Moscow, Russia.
³¹ Center for Relativistic Astrophysics and High Energy Physics, School of Physics and Materials Science & Institute of Space Science and Technology, Nanchang University, 330031 Nanchang, Jiangxi, China.
³² National Space Science Center, Chinese Academy of Sciences, 100190 Beijing, China.

PMID: 37897763
DOI: 10.1103/PhysRevLett.131.151001

Abstract

The diffuse Galactic γ-ray emission, mainly produced via interactions between cosmic rays and the interstellar medium and/or radiation field, is a very important probe of the distribution, propagation, and interaction of cosmic rays in the Milky Way. In this Letter, we report the measurements of diffuse γ rays from the Galactic plane between 10 TeV and 1 PeV energies, with the square kilometer array of the Large High Altitude Air Shower Observatory (LHAASO). Diffuse emissions from the inner (15°<l<125°, |b|<5°) and outer (125°<l<235°, |b|<5°) Galactic plane are detected with 29.1σ and 12.7σ significance, respectively. The outer Galactic plane diffuse emission is detected for the first time in the very- to ultra-high-energy domain (E>10 TeV). The energy spectrum in the inner Galaxy regions can be described by a power-law function with an index of -2.99±0.04, which is different from the curved spectrum as expected from hadronic interactions between locally measured cosmic rays and the line-of-sight integrated gas content. Furthermore, the measured flux is higher by a factor of ∼3 than the prediction. A similar spectrum with an index of -2.99±0.07 is found in the outer Galaxy region, and the absolute flux for 10≲E≲60 TeV is again higher than the prediction for hadronic cosmic ray interactions. The latitude distributions of the diffuse emission are consistent with the gas distribution, while the longitude distributions show clear deviation from the gas distribution. The LHAASO measurements imply that either additional emission sources exist or cosmic ray intensities have spatial variations.

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Measurement of Ultra-High-Energy Diffuse Gamma-Ray Emission of the Galactic Plane from 10 TeV to 1 PeV with LHAASO-KM2A

Affiliations

Measurement of Ultra-High-Energy Diffuse Gamma-Ray Emission of the Galactic Plane from 10 TeV to 1 PeV with LHAASO-KM2A

Authors

Affiliations

Abstract

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