http://arxiv.org/abs/1412.4716
Anisotropy in the arrival direction distribution of ultrahigh-energy cosmic rays (UHECRs) produced by powerful sources is numerically evaluated. Nondetection of significant anisotropy at $\approx 10^{19}$ eV at present and in future experiments imposes upper limits on UHECR proton luminosity of steady sources as a function of source redshift. The upper limits constrain the existence of typical sources in the local universe and provide strong limits on the local density $\gtrsim 10^{-2.5}$ Mpc$^{-3}$ of $10^{19}$ eV UHECR sources, assuming average intergalactic magnetic field less than $10^{-9}$ G. This isotropy, which is stronger than measured at the highest energies, may indicate the transient generation of UHECRs. Our anisotropy calculations are applied for extreme high-frequency-peaked BL Lac objects 1ES 0229+200, 1ES 1101-232, and 1ES 0347-121, to test the UHECR-induced cascade model, in which beamed UHECR protons generate TeV radiation in transit from sources. The isotropy constraints on the UHECR-induced cascade model are stronger than the cosmic-ray luminosity bounds obtained from $\gamma$-ray observations, depending on the magnetic-field structure surrounding the Milky Way. The effects of the Galactic and local extragalactic magnetic fields to the UHECR anisotropy are investigated. If extragalactic magnetic fields are weak enough for UHECRs to remain beamed, significant UHECR anisotropy from these blazars should be detectable by the Pierre Auger Observatory unless the maximum energy of UHECRs is well below $10^{19}$ eV. If these are the sources of UHECRs above $10^{19}$ eV, a local magnetic structure surrounding the Milky Way would have to produce the observed isotropy at $\sim 10^{19}$ eV.
H. Takami, K. Murase and C. Dermer
Tue, 16 Dec 14
63/78
Comments: 15 pages, 10 figures
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