2017/09/30 by Noemie Globus, Tsvi Piran · 21 citations
Physics and Astronomy · #Amplitude #Anisotropy #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Dark Matter and Cosmic Phenomena #Dipole #Field (mathematics) #Intergalactic travel #Magnetic dipole #Magnetic field #Photodisintegration #astro-ph.HE
paper · pdf · doi:10.3847/2041-8213/aa991b
published in The Astrophysical Journal Letters 850(2), L25 (IOP Publishing) · 6 pages, 5 figures, accepted in ApJ Letters
openalex created_date 2017/10/06 · arxiv created 2017/11/16 · openalex publication_date 2017/11/22 · arxiv updated 2017/12/06 · openalex updated_date 2026/08/06
Abstract We explore the possibility that the recently detected dipole anisotropy in the arrival directions of >8 EeV ultra-high-energy cosmic-rays (UHECRs) arises due to the large-scale structure. We assume that the cosmic-ray sources follow the matter distribution and calculate the flux-weighted UHECRs’ rms dipole amplitude taking into account the diffusive transport in the intergalactic magnetic field (IGMF). We find that the flux-weighted rms dipole amplitude is ∼8% before entering the Galaxy. The amplitude in the [4–8] EeV is only slightly lower ∼5%. The required IGMF is of the order of 5–30 nG, and the UHECR sources must be relatively nearby, within ∼300 Mpc. The absence of a statistically significant signal in the lower-energy bin can be explained if the same nuclei specie dominates the composition in both energy bins and diffusion in the Galactic magnetic field reduces the dipole of these lower-rigidity particles. Photodisintegration of higher-energy UHECRs could also reduce somewhat the lower-energy dipole.