Foteini Oikonomou, Amy Connolly, Filipe B. Abdalla, Ofer Lahav, Shaun A. Thomas, David Waters, Eli Waxman
We study the arrival directions of 69 ultra-high energy cosmic rays (UHECRs) observed at the Pierre Auger Observatory (PAO) with energies exceeding 55 EeV. We investigate whether the UHECRs exhibit the anisotropy signal expected if the primary particles are protons that originate in galaxies in the local universe, or in sources correlated with these galaxies. We cross-correlate the UHECR angular positions with the positions of IRAS-PSCz and 2MASS-6dF galaxies (with median depth of 120 and 225 Mpc respectively) weighted for GZK and other particle propagation effects. This is the first time that the 6dF survey is used for a study of this type and the first time that the PSCz survey is used with the full 69 publicly released PAO events. We find the probability that the observed UHECR events are consistent with an isotropic hypothesis to be less than 5% for most of the parameter space considered. The observed correlation is consistent with the mean of the model distribution of UHECRs associated with PSCz and 6dF galaxies. The agreement in results between the two catalogues, which probe similar large scale structure, is very good. Finally, we explore how the random magnetic deflections of UHECRs during propagation affect the expected anisotropy signal.
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http://arxiv.org/abs/1207.4043
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