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Journal of Cosmology and Astroparticle Physics 19 (2004) 08
Angular Power Spectrum Estimation of Cosmic Ray Anisotropies with Full or Partial Sky Coverage
O. Deligny1, 2, E. Armengaud1, 2, T. Beau1, 2, P. Da Silva, J.-Ch. Hamilton3, C. Lachaud1, 2, A. Letessier-Selvon3, Benoît Revenu1, 2
For the PIERRE AUGER collaboration(s)

We study the angular power spectrum estimate in order to search for large scale anisotropies in the arrival directions distribution of the highest-energy cosmic rays. We show that this estimate can be performed even in the case of partial sky coverage and validated over the full sky under the assumption that the observed fluctuations are statistically spatial stationary. If this hypothesis - which can be tested directly on the data - is not satisfied, it would prove, of course, that the cosmic ray sky is non isotropic but also that the power spectrum is not an appropriate tool to represent its anisotropies, whatever the sky coverage available. We apply the method to simulations of the Pierre Auger Observatory, reconstructing an input power spectrum with the Southern site only and with both Northern and Southern ones. Finally, we show the improvement that a full-sky observatory brings to test an isotropic distribution, and we discuss the sensitivity of the Pierre Auger Observatory to large scale anisotropies.
1:  APC - UMR 7164 - AstroParticule et Cosmologie
2:  PCC - Physique Corpusculaire et Cosmologie - Collège de France
3:  LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
Physics/Astrophysics/Cosmology and Extra-Galactic Astrophysics

Sciences of the Universe/Astrophysics
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