A high-significance detection of non-Gaussianity in the WMAP 3-yr data using directional spherical wavelets

Abstract

Abstract We repeat the directional spherical real Morlet wavelet analysis, used to detect non-Gaussianity in the Wilkinson Microwave Anisotropy Probe (WMAP) 1-yr data, on the WMAP 3-yr data. The non-Gaussian signal previously detected is indeed present in the 3-yr data, although the significance of the detection is reduced. Using our most conservative method for constructing significance measures, we find that the significance of the detection of non-Gaussianity drops from 98.3 ± 0.4 to 94.9 ± 0.7 per cent; the significance drops from 99.3 ± 0.3 to 97.2 ± 0.5 per cent using a method based on the χ2 statistic. The wavelet analysis allows us to localize most likely sources of non-Gaussianity on the sky. We detect very similar localized regions in the WMAP 1-yr and 3-yr data, although the regions extracted appear more pronounced in the 3-yr data. When all localized regions are excluded from the analysis, the 3-yr data are consistent with Gaussianity.