Isotropy constraints on powerful sources of ultrahigh-energy cosmic rays at 10{sup 19} eV
- Theory Center, Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK), 1-1, Oho, Tsukuba, Ibaraki 305-0801 (Japan)
- Institute for Advanced Study, 1 Einstein Drive, Princeton, New Jersey 08540 (United States)
- Code 7653, Space Science Division, U.S. Naval Research Laboratory, Washington, DC 20375 (United States)
Anisotropy in the arrival direction distribution of ultrahigh-energy cosmic rays (UHECRs) produced by powerful sources is numerically evaluated. We show that nondetection of significant anisotropy at ≈10{sup 19} eV at present and in future experiments imposes general upper limits on UHECR proton luminosity of steady sources as a function of source redshifts. The upper limits constrain the existence of typical steady 10{sup 19} eV UHECR sources in the local universe and limit their local density to ≳10{sup −3} Mpc {sup −3}, assuming average intergalactic magnetic fields less than 10{sup −9} G. This isotropy, being stronger than that measured at the highest energies, may indicate the transient generation of UHECRs. Our calculations are applied for extreme high-frequency-peaked BL Lacertae 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. While the magnetic-field structure surrounding the sources affects the required absolute cosmic-ray luminosity of the blazars, the magnetic-field structure surrounding the Milky Way directly affects the observed anisotropy. If these magnetic fields are weak enough, significant UHECR anisotropy from these blazars is detectable by the Pierre Auger Observatory unless the maximum energy of UHECR protons is below 10{sup 19} eV. Furthermore, if these are the sources of UHECRs above 10{sup 19} eV, a local magnetic structure surrounding the Milky Way is needed to explain the observed isotropy at ∼10{sup 19} eV, which may be incompatible with large magnetic structures around all galaxies for the UHECR-induced cascade model to work with reasonable jet powers.
- OSTI ID:
- 22887117
- Journal Information:
- Astrophysical Journal, Vol. 817, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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