Origin and Propagation of Ultra-High Energy Cosmic Rays

The existence of cosmic ray particles up to the ultra-high energy limit (> 10^20 eV) is now beyond any doubt. The detection of cosmic particles with such energies imposes a challenge for the comprehension of their sources and nature. On one side, particles with such high energies are difficult to be produced by any astrophysical source. On the other side, the interactions of these particles with photons of the cosmic microwave background cause substantial losses of energy which constraint the maximum distances that the particles are able to travel from the sources to the detectors. Aiming to help to elucidate the problem of UHECR source identification, we have performed 3-D simulations of particle trajectories propagated through the stochastic intergalactic and an extended Galactic halo magnetic fields. Going further, we have also performed simulations of proton and Fe nuclei through the spiral Galactic magnetic field (GMF) and built full-sky maps of their arrival direction distribution in both the detector (after deflection in the GMF) and just outside the Galaxy. In this work we summarize the main results of these investigations.