Ultrahigh energy cosmic rays in a structured and magnetized universe

We simulate propagation of cosmic ray nucleons above 10(19) eV in scenarios where both the source distribution and magnetic fields within about 50 Mpc from us are obtained from an unconstrained large scale structure simulation. We find that a consistency of predicted sky distributions with current data above 4x10(19) eV requires magnetic fields of similar or equal to0.1 muG in our immediate environment, and a nearby source density of similar to10(-4)-10(-3) Mpc(-3). Radio galaxies could provide the required sources, but only if both high- and low-luminosity radio galaxies are very efficient cosmic ray accelerators. Moreover, at similar or equal to10(19) eV an additional isotropic flux component, presumably of cosmological origin, should dominate over the local flux component by about a factor of 3 in order to explain the observed isotropy. This argues against the scenario in which local astrophysical sources of cosmic rays above similar or equal to10(19) eV reside in a strongly magnetized (Bsimilar or equal to0.1 muG) and structured intergalactic medium. Finally we discuss how future large scale full-sky detectors such as the Pierre Auger project will allow us to put much more stringent constraints on source and magnetic field distributions.