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Journal of Cosmology and Astroparticle Physics 02 (2008) 009
Estimates of multipolar coefficients to search for cosmic ray anisotropies with non-uniform or partial sky coverage
P. Billoir1, O. Deligny2

We study the possibility to extract the multipolar moments of an underlying distribution from a set of cosmic rays observed with non-uniform or even partial sky coverage. We show that if the degree is assumed to be upper bounded by $L$, each multipolar moment can be recovered whatever the coverage, but with a variance increasing exponentially with the bound $L$ if the coverage is zero somewhere. Despite this limitation, we show the possibility to test predictions of a model without any assumption on $L$ by building an estimate of the covariance matrix seen through the exposure function.
1 :  LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
2 :  IPNO - Institut de Physique Nucléaire d'Orsay
Physique/Astrophysique/Cosmologie et astrophysique extra-galactique

Planète et Univers/Astrophysique
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