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Constraining the Cosmic-ray Energy Based on Observations of Nearby Galaxy Clusters by LHAASO

The LHAASO Collaboration, Zhen Cao, F. Aharonian, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, W. Bian, J. Blunier, A. V. Bukevich, C. M. Cai, Y. Y. Cai, W. Y. Cao, Zhe Cao, J. Chang, J. F. Chang, E. S. Chen, G. H. Chen, H. K. Chen, L. F. Chen, Liang Chen, Long Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. Chen, S. H. Chen, S. Z. Chen, T. L. Chen, X. B. Chen, X. J. Chen, X. P. Chen, Y. Chen, N. Cheng, Q. Y. Cheng, Y. D. Cheng, M. Y. Cui, S. W. Cui, X. H. Cui, Y. D. Cui, B. Z. Dai, H. L. Dai, Z. G. Dai, Danzengluobu, Y. X. Diao, A. J. Dong, X. Q. Dong, K. K. Duan, J. H. Fan, Y. Z. Fan, J. Fang, J. H. Fang, K. Fang, C. F. Feng, H. Feng, L. Feng, S. H. Feng, X. T. Feng, Y. Feng, Y. L. Feng, S. Gabici, B. Gao, Q. Gao, W. Gao, W. K. Gao, M. M. Ge, T. T. Ge, L. S. Geng, G. Giacinti, G. H. Gong, Q. B. Gou, M. H. Gu, F. L. Guo, J. Guo, K. J. Guo, X. L. Guo, Y. Q. Guo, Y. Y. Guo, R. P. Han, O. A. Hannuksela, M. Hasan, H. H. He, H. N. He, J. Y. He, X. Y. He, Y. He, S. Hernández-Cadena, B. W. Hou, C. Hou, X. Hou, H. B. Hu, S. C. Hu, C. Huang, D. H. Huang, J. J. Huang, X. L. Huang, X. T. Huang, X. Y. Huang, Y. Huang, Y. Y. Huang, A. Inventar, X. L. Ji, H. Y. Jia, K. Jia, H. B. Jiang, K. Jiang, X. W. Jiang, Z. J. Jiang, M. Jin, S. Kaci, M. M. Kang, I. Karpikov, D. Khangulyan, D. Kuleshov, K. Kurinov, Cheng Li, Cong Li, D. Li, F. Li, H. B. Li, H. C. Li, Jian Li, Jie Li, K. Li, L. Li, R. L. Li, S. D. Li, T. Y. Li, W. L. Li, X. R. Li, Xin Li, Y. Li, Zhe Li, Zhuo Li, E. W. Liang, Y. F. Liang, S. J. Lin, B. Liu, C. Liu, D. Liu, D. B. Liu, H. Liu, J. Liu, J. L. Liu, J. R. Liu, M. Y. Liu, R. Y. Liu, S. M. Liu, W. Liu, X. Liu, Y. Liu, Y. Liu, Y. N. Liu, Y. Q. Lou, Q. Luo, Y. Luo, H. K. Lv, B. Q. Ma, L. L. Ma, X. H. Ma, I. O. Maliy, J. R. Mao, Z. Min, W. Mitthumsiri, Y. Mizuno, G. B. Mou, A. Neronov, K. C. Y. Ng, M. Y. Ni, L. Nie, L. J. Ou, Z. W. Ou, P. Pattarakijwanich, Z. Y. Pei, D. Y. Peng, J. C. Qi, M. Y. Qi, J. J. Qin, D. Qu, A. Raza, C. Y. Ren, D. Ruffolo, A. Sáiz, D. Savchenko, D. Semikoz, L. Shao, O. Shchegolev, Y. Z. Shen, X. D. Sheng, Z. D. Shi, F. W. Shu, H. C. Song, Yu. V. Stenkin, V. Stepanov, Y. Su, D. X. Sun, H. Sun, J. X. Sun, Q. N. Sun, X. N. Sun, Z. B. Sun, N. H. Tabasam, J. Takata, P. H. T. Tam, H. B. Tan, Q. W. Tang, R. Tang, Z. B. Tang, W. W. Tian, C. N. Tong, L. H. Wan, C. Wang, D. H. Wang, G. W. Wang, H. G. Wang, J. C. Wang, K. Wang, Kai Wang, Kai Wang, L. P. Wang, L. Y. Wang, L. Y. Wang, R. Wang, W. Wang, X. G. Wang, X. J. Wang, X. Y. Wang, Y. Wang, Y. D. Wang, Z. H. Wang, Z. X. Wang, Zheng Wang, D. M. Wei, J. J. Wei, Y. J. Wei, T. Wen, S. S. Weng, C. Y. Wu, H. R. Wu, Q. W. Wu, S. Wu, X. F. Wu, Y. S. Wu, S. Q. Xi, J. Xia, J. J. Xia, G. M. Xiang, D. X. Xiao, G. Xiao, Y. F. Xiao, Y. L. Xin, H. D. Xing, Y. Xing, D. R. Xiong, B. N. Xu, C. Y. Xu, D. L. Xu, R. F. Xu, R. X. Xu, S. S. Xu, W. L. Xu, L. Xue, D. H. Yan, T. Yan, C. W. Yang, C. Y. Yang, F. F. Yang, L. L. Yang, M. J. Yang, R. Z. Yang, W. X. Yang, Z. H. Yang, Z. G. Yao, X. A. Ye, L. Q. Yin, N. Yin, X. H. You, Z. Y. You, Q. Yuan, H. Yue, H. D. Zeng, T. X. Zeng, W. Zeng, X. T. Zeng, M. Zha, B. B. Zhang, B. T. Zhang, C. Zhang, H. Zhang, H. M. Zhang, H. Y. Zhang, J. L. Zhang, J. Y. Zhang, Li Zhang, P. F. Zhang, R. Zhang, S. R. Zhang, S. S. Zhang, S. Y. Zhang, W. Zhang, W. Y. Zhang, X. Zhang, X. P. Zhang, Yi Zhang, Yong Zhang, Z. P. Zhang, J. Zhao, L. Zhao, L. Z. Zhao, S. P. Zhao, X. H. Zhao, Z. H. Zhao, F. Zheng, T. C. Zheng, B. Zhou, H. Zhou, J. N. Zhou, M. Zhou, P. Zhou, R. Zhou, X. X. Zhou, X. X. Zhou, B. Y. Zhu, C. G. Zhu, F. R. Zhu, H. Zhu, K. J. Zhu, Y. C. Zou, X. Zuo

TL;DR

This work uses LHAASO WCDA and KM2A data to search for diffuse γ-ray emission from three nearby galaxy clusters (Coma, Perseus, Virgo) and models extended emission as disks within $R_{500}$. No significant emission is detected, yielding stringent 95% C.L. upper limits in the $1-25\, \mathrm{TeV}$ and $>25\, \mathrm{TeV}$ bands, which translate into model-independent constraints on the Crp energy budget above $10\,\mathrm{TeV}$. By translating these γ-ray limits into $X_{\text{CRp}} = E_{\text{CRp}}/E_{\text{th}}$ under various CRp spectral indices and DSA scenarios (linear and nonlinear), the paper places tight bounds on high-energy CR populations and UHECR content in clusters. The absence of annulus-like emissions argues against efficient $p\gamma$-IC production from UHECRs accelerated in cluster merger shocks, while the results are complementary to radio-based constraints and will improve with future LHAASO data and neutrino observations, advancing our understanding of CR acceleration and transport in large-scale structures.

Abstract

Galaxy clusters act as reservoirs of high-energy cosmic rays (CRs). As CRs propagate through the intracluster medium, they generate diffuse $γ$-rays detectable by arrays such as LHAASO. These $γ$-rays result from proton-proton ($pp$) collisions of very high-energy cosmic rays (VHECRs) or inverse Compton (IC) scattering of positron-electron pairs created by $pγ$ interactions of ultra-high-energy cosmic rays (UHECRs). We analyzed diffuse $γ$-ray emission from the Coma, Perseus, and Virgo clusters using LHAASO data. Diffuse emission was modeled as a disk of radius $R_{500}$ for each cluster while accounting for point sources. No significant diffuse emission was detected, yielding 95\% confidence level (C.L.) upper limits on the $γ$-ray flux: for WCDA (1-25~TeV) and KM2A ($>25$~TeV), less than $(49.4, 13.7, 54.0)$ and $(1.34, 1.14, 0.40) \times 10^{-14}$~ph~cm$^{-2}$~s$^{-1}$ for Coma, Perseus, and Virgo, respectively. The $γ$-ray upper limits can be used to derive model-independent constraints on the integral energy of CRp above 10~TeV (corresponding to the LHAASO observational range $>1$~TeV under the $pp$ scenario) to be less than $(1.96, 0.59, 0.08) \times 10^{61}$~erg. The absence of detectable annuli/ring-like structures, indicative of cluster accretion or merging shocks, imposes further constraints on models in which the UHECRs are accelerated in the merging shocks of galaxy clusters.

Constraining the Cosmic-ray Energy Based on Observations of Nearby Galaxy Clusters by LHAASO

TL;DR

This work uses LHAASO WCDA and KM2A data to search for diffuse γ-ray emission from three nearby galaxy clusters (Coma, Perseus, Virgo) and models extended emission as disks within . No significant emission is detected, yielding stringent 95% C.L. upper limits in the and bands, which translate into model-independent constraints on the Crp energy budget above . By translating these γ-ray limits into under various CRp spectral indices and DSA scenarios (linear and nonlinear), the paper places tight bounds on high-energy CR populations and UHECR content in clusters. The absence of annulus-like emissions argues against efficient -IC production from UHECRs accelerated in cluster merger shocks, while the results are complementary to radio-based constraints and will improve with future LHAASO data and neutrino observations, advancing our understanding of CR acceleration and transport in large-scale structures.

Abstract

Galaxy clusters act as reservoirs of high-energy cosmic rays (CRs). As CRs propagate through the intracluster medium, they generate diffuse -rays detectable by arrays such as LHAASO. These -rays result from proton-proton () collisions of very high-energy cosmic rays (VHECRs) or inverse Compton (IC) scattering of positron-electron pairs created by interactions of ultra-high-energy cosmic rays (UHECRs). We analyzed diffuse -ray emission from the Coma, Perseus, and Virgo clusters using LHAASO data. Diffuse emission was modeled as a disk of radius for each cluster while accounting for point sources. No significant diffuse emission was detected, yielding 95\% confidence level (C.L.) upper limits on the -ray flux: for WCDA (1-25~TeV) and KM2A (~TeV), less than and ~ph~cm~s for Coma, Perseus, and Virgo, respectively. The -ray upper limits can be used to derive model-independent constraints on the integral energy of CRp above 10~TeV (corresponding to the LHAASO observational range ~TeV under the scenario) to be less than ~erg. The absence of detectable annuli/ring-like structures, indicative of cluster accretion or merging shocks, imposes further constraints on models in which the UHECRs are accelerated in the merging shocks of galaxy clusters.

Paper Structure

This paper contains 8 sections, 2 equations, 3 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Facts of the galaxy clusters
  3. Data analysis
  4. Analysis method
  5. Results
  6. Discussion and Conclusion
  7. Detailed Information OF THESE GALAXY CLUSTERS
  8. EBL model

Figures (3)

  • Figure 1: The upper panel shows the WCDA skymaps (1-25 TeV) with the contribution of known point sources subtracted, while the lower panel displays the KM2A skymaps ($>$ 25 TeV). From left to right, they correspond to the Coma, Perseus, and Virgo clusters. The $R_{500}$ radius of these clusters is respectively indicated by gray dashed lines. The known $\gamma$-rays point sources NGC 1275 and IC 310 in the Perseus cluster are respectively marked with cyan squares and upward triangles, while M87 in the Virgo cluster is indicated by a green star.
  • Figure 2: Left panel: The 95% C.L. flux upper limits for the extended emission within the $R_{500}$ radius of the three galaxy clusters, after correction for the EBL, are presented. The darker-blue and lighter-blue arrows represent the data from WCDA and KM2A, respectively. The gray solid and dashed lines represent the $\gamma$-ray fluxes scaled to the strongest constraint for the IC process of secondary electrons produced by the $p-\gamma$ interactions of accelerated cosmic rays with linear and nonlinear DSA scenarios, respectively, as shown in Figs. 7 and 13 of vannoniAccelerationRadiationUltrahigh2011. The blue dashed line represents the $\gamma$-ray flux scaled to the strongest constraint for hadronic processes. From top to bottom, the corresponding clusters are the Coma, Perseus, and Virgo clusters. Right panel: The 95% C.L. upper-limit constraints on $X_{\text{CRp}}$ for these three galaxy clusters, under the hypothesis of different CRp spectral indices, are shown. The sequence of galaxy clusters from top to bottom is consistent with the order presented in the left panel. The solid squares in the first plot on the right panel represent the strongest constraints (99% C.L.) previously obtained by HESS thehesscollaborationConstraintsMultiTeVParticle2009. The hollow pentagrams and crosses represent VERITAS's and Fermi's strongest constraints (99% C.L.) on $X_{\text{CRp}}$ within the virial radius of Coma arlenCONSTRAINTSCOSMICRAYS2012. The hollow circles in the second plot on the right denote the 95% C.L. constraints on $X_{\text{CRp}}$ within the virial radius of the Perseus cluster, as determined by MAGIC magiccollaborationDeepObservationNGC2016. The hollow squares in the bottom-most plot represent the 99.7% C.L. constraints on $X_{\text{CRp}}$ within the Virgo cluster at $\sim 20 \, \text{kpc}$, as determined by HESS collaborationConstrainingCosmicrayPressure2023c. In the bottom two panels, the open crosses represent the 95% C.L. upper limits provided by Fermi ackermannGeVGAMMARAYFLUX2010.
  • Figure B.1: The EBL absorption efficiency for each of the three galaxy clusters. Coma is represented by dotted line, Perseus by dashed line, and Virgo by solid line.