Non‐Gaussianity detections in the Bianchi VII h corrected WMAP one‐year data made with directional spherical wavelets

Many of the current anomalies reported in the WMAP text ( WMAP ) one‐year data disappear after ‘correcting’ for the best‐fitting embedded Bianchi type VII h component, albeit assuming no dark energy component. We investigate the effect of this Bianchi correction on the detections of non‐Gaussianity in the WMAP data that we previously made using directional spherical wavelets. We confirm that the deviations from Gaussianity in the kurtosis of spherical Mexican hat wavelet coefficients are eliminated once the data are corrected for the Bianchi component, as previously discovered by Jaffe et al. This is due to the reduction of the cold spot at Galactic coordinates ( l , b ) = (209°, −57°) , which Cruz et al. claimed to be the sole source of non‐Gaussianity introduced in the kurtosis. Our previous detections of non‐Gaussianity observed in the skewness of spherical wavelet coefficients are not reduced by the Bianchi correction. Indeed, the most significant detection of non‐Gaussianity made with the spherical real Morlet wavelet at a significant level of 98.4 per cent remains (using a very conservative method to estimate the significance). Furthermore, we perform preliminary tests to determine if foregrounds or systematics are the source of this non‐Gaussian signal, concluding that it is unlikely that these factors are responsible. We make our code to simulate Bianchi‐induced temperature fluctuations publicly available.