Alignment tests for low CMB multipoles

Abstract

We investigate the large scale anomalies in the angular distribution of the cosmic microwave background radiation as measured by WMAP using several tests. These tests, based on the multipole vector expansion, measure correlations between the phases of the multipoles as expressed by the directions of the multipole vectors and their associated normal planes. We have computed the probability distribution functions for 46 such tests, for the multipoles l=2-5. We confirm earlier findings that point to a high level of alignment between l=2 (quadrupole) and l=3 (octopole), but with our tests we do not find significant planarity in the octopole. In addition, we have found other possible anomalies in the alignment between the octopole and the l=4 (hexadecupole) components, as well as in the planarity of l=4 and l=5. We introduce the notion of a total likelihood to estimate the relevance of the low-multipoles tests of non-gaussianity. We show that, as a result of these tests, the CMB maps which are most widely used for cosmological analysis lie within the ~ 10% of randomly generated maps with lowest likelihoods.

References added, updated discussion on alignment with Ecliptic Plane. 12 Pages, 6 Figures. Results for additional maps, the normalized frequencies for the tests and a Mathematica Notebook that computes the tests can be found on http://fma.if.usp.br/~abramo/MVA.html

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