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Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE
Abstract:
Recent results of the Pierre Auger (Auger) fluorescence detectors indicate an
increasingly heavy composition of ultra-high energy (UHE) cosmic rays (CRs).
Assuming that this trend continues up to the highest energies observed by the
Auger surface detectors we derive the constraints this places on the local
source distribution of UHE CR nuclei. Utilizing an analytic description of UHE
CR propagation we derive the expected spectra and composition for a wide range
of source emission spectra. We find that sources of intermediate-to-heavy
nuclei are consistent with the observed spectra and composition data above the
ankle. This consistency requires the presence of nearby sources within 60 Mpc
and 80 Mpc for silicon and iron only sources, respectively. The necessity of
these local sources becomes even more compelling in the presence nano-Gauss
local extragalactic magnetic fields.
