An Upper Limit on the Strength of the Extragalactic Magnetic Field from Ultra-high-energy Cosmic-Ray Anisotropy

If ultra-high-energy cosmic rays originate from extragalactic sources, the offsets of their arrival directions from these sources imply an upper limit on the strength of the extragalactic magnetic field (EGMF). The Pierre Auger Collaboration has recently reported that anisotropy in the arrival direc...

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Bibliographic Details
Published in:The Astrophysical journal 2018-07, Vol.861 (1), p.3
Main Authors: Bray, J. D., Scaife, A. M. M.
Format: Article
Language:English
Subjects:
Anisotropy
astroparticle physics
Astrophysics
Augers
Cosmic ray anisotropy
Cosmic ray composition
Cosmic rays
Gamma rays
Magnetic fields
Offsets
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Summary:If ultra-high-energy cosmic rays originate from extragalactic sources, the offsets of their arrival directions from these sources imply an upper limit on the strength of the extragalactic magnetic field (EGMF). The Pierre Auger Collaboration has recently reported that anisotropy in the arrival directions of cosmic rays is correlated with several types of extragalactic objects. If these cosmic rays originate from these objects, they imply a limit on the EGMF strength of B < 0.7- G for coherence lengths λB < 100 Mpc and B < 0.7-2.2 × 10−10 G at larger scales. This is comparable to existing upper limits at λB = 1 Mpc, and improves on them by a factor of 4-12 at larger scales. The principal source of uncertainty in our results is the unknown cosmic-ray composition.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aac777