Mapping possible non-Gaussianity in the Planck maps

¹ Observatório Nacional, Rua General José Cristino 77, 20921-400 Rio de Janeiro – RJ, Brazil
e-mail: bernui@on.br
² Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro – RJ, Brazil
e-mail: reboucas@cbpf.br

Received: 22 July 2014
Accepted: 6 October 2014

Abstract

Context. The study of the non-Gaussianity of the temperature fluctuations of cosmic background radiation (CMB) can be used to break the degeneracy between the inflationary models and to test alternative scenarios of the early universe. However, there are several sources of non-Gaussian contaminants in the CMB data, which make a convincing extraction of primordial non-Gaussianity into an ambitious observational and statistical enterprise. 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.

Aims. Here we address the question of how previous recent analyses of Gaussianity of WMAP maps are modified if the nearly full-sky foreground-cleaned Planck maps are used, therefore extending and complementing such an examination in several regards.

Methods. Once 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 when masking the foreground-cleaned Planck maps with the inpmask, valmask, and U73 Planck masks.

Results. 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 the large-angle anomalies reported by the Planck team. Finally, we examine the robustness of the Gaussianity analyses with respect to the real pixel’s noise as given by the Planck team, and show that no appreciable changes arise when it is incorporated into the maps. The results of our analyses provide important information concerning Gaussianity of the foreground-cleaned Planck maps when diverse cut-sky masks are used.