Linking high-energy cosmic particles by black-hole jets embedded in large-scale structures


The origin of ultrahigh-energy cosmic rays (UHECRs) is a half-century-old enigma1. The mystery has been deepened by an intriguing coincidence: over ten orders of magnitude in energy, the energy generation rates of UHECRs, PeV neutrinos and isotropic sub-TeV γ-rays are comparable, which hints at a grand unified picture2. Here we report that powerful black hole jets in aggregates of galaxies can supply the common origin for all of these phenomena. Once accelerated by a jet, low-energy cosmic rays confined in the radio lobe are adiabatically cooled; higher-energy cosmic rays leaving the source interact with the magnetized cluster environment and produce neutrinos and γ-rays; the highest-energy particles escape from the host cluster and contribute to the observed cosmic rays above 100 PeV. The model is consistent with the spectrum, composition and isotropy of the observed UHECRs, and also explains the IceCube neutrinos and the non-blazar component of the Fermi γ-ray background, assuming a reasonable energy output from black hole jets in clusters.

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Fig. 1: Extragalactic multi-messenger (UHECR, high-energy neutrino and γ-ray) background spectra.
Fig. 2: Mean of the maximum depth of an air shower of UHECRs.


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We thank R. Alves Batista, M. Bustamante, M. Coleman Miller, C. Reynolds and M. Unger for helpful comments. This work made use of supercomputing resources at the University of Maryland. We gratefully acknowledge support from the Eberly College of Science of Penn State University and the Institute for Gravitation and the Cosmos. The work of K.M. is supported by Alfred P. Sloan Foundation and NSF grant No. PHY-1620777.

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K.F. performed simulations and produced the figures. K.M. designed the research and contributed to the calculations. Both authors edited the manuscript.

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Correspondence to Kohta Murase.

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Fang, K., Murase, K. Linking high-energy cosmic particles by black-hole jets embedded in large-scale structures. Nature Phys 14, 396–398 (2018).

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