Mapping possible non-Gaussianity in the Planck maps

TL;DR

This paper investigates the Gaussianity of Planck CMB maps using a patch-based skewness and kurtosis method, revealing that masking and noise considerations significantly influence the detection of non-Gaussian features.

Contribution

It extends previous WMAP analyses to Planck data, comparing different masks and noise effects to assess the Gaussianity of foreground-cleaned CMB maps.

Findings

Planck maps show deviations from Gaussianity with less severe masks.

Masking with the U73 mask yields results consistent with Gaussianity.

Noise inclusion does not significantly alter Gaussianity analysis outcomes.

Abstract

[Abridged.] It is conceivable that no single statistical estimator can be sensitive to all forms and levels of non-Gaussianity that may be present in observed CMB data. In recent works a statistical procedure based upon the calculation of the skewness and kurtosis of the patches of CMB sky-sphere has been proposed and used to find out significant large-angle deviation from Gaussianity in the foreground-reduced WMAP maps. Here we address the question as to how the analysis of Gaussianity of WMAP maps is modified if the foreground-cleaned Planck maps are used, therefore extending and complementing the previous analyses in several regards. We carry out a new analysis of Gaussianity with the available nearly full-sky foreground-cleaned Planck maps. As the foregrounds are cleaned through different component separation procedures, each of the resulting Planck maps is then tested for Gaussianity. We determine quantitatively the effects for Gaussianity of masking the foreground-cleaned Planck maps with the INPMASK, VALMASK, and U73 Planck masks. We show that although the foreground-cleaned Planck maps present significant deviation from Gaussianity of different degrees when the less severe INPMASK and VALMASK are used, they become consistent with Gaussianity as detected by our indicator $S$ when masked with the union U73 mask. A slightly smaller consistency with Gaussianity is found when the $K$ indicator is employed, which seems to be associated with large-angle anomalies reported by the Planck team. Finally, we examine the robustness of the Gaussianity analyses with respect to the noise pixel's as given by the Planck team, and show that no appreciable changes arise when is incorporated into the maps. The results of our analyses provide important information about the suitability of the foreground-cleaned Planck maps as Gaussian reconstructions of the CMB sky.