# Estimates of multipolar coefficients to search for cosmic ray anisotropies with non-uniform or partial sky coverage

Abstract : 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.
Document type :
Journal articles
Domain :

http://hal.in2p3.fr/in2p3-00178861
Contributor : Dominique Girod <>
Submitted on : Friday, October 12, 2007 - 1:11:05 PM
Last modification on : Thursday, December 10, 2020 - 12:32:43 PM

### Citation

P. Billoir, O. Deligny. Estimates of multipolar coefficients to search for cosmic ray anisotropies with non-uniform or partial sky coverage. Journal of Cosmology and Astroparticle Physics, Institute of Physics (IOP), 2008, 02, pp.009. ⟨10.1088/1475-7516/2008/02/009⟩. ⟨in2p3-00178861⟩

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