Angular Power Spectrum Estimation of Cosmic Ray Anisotropies with Full or Partial Sky Coverage

Abstract

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.

16 pages, 6 figures, version accepted for publication by JCAP

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Cited by in corpus (9)

• Searching for a Correlation Between Cosmic-Ray Sources Above 10^{19} eV and Large-Scale Structure
• Eternal Inflation with alpha'-Corrections
• Ultrahigh Energy Nuclei Propagation in a Structured, Magnetized Universe
• Multi-resolution anisotropy studies of ultrahigh-energy cosmic rays detected at the Pierre Auger Observatory
• Generalised 3D-reconstruction method of a dipole anisotropy in cosmic-ray distributions
• Measurements and implications of cosmic ray anisotropies from TeV to trans-EeV energies
• Prospects of detecting a large-scale anisotropy of ultra-high-energy cosmic rays from a nearby source with the K-EUSO orbital telescope
• The signature of local cosmic structures on the ultra-high energy cosmic ray anisotropies
• Large-scale anisotropies of ultra-high-energy cosmic rays measured at the Pierre Auger Observatory