Gaussianity test of Planck CMB polarization data using the statistics of unpolarized points (Part I)

TL;DR

This paper introduces a robust method to test the Gaussianity of Planck CMB polarization data by analyzing unpolarized points, revealing significant non-Gaussian features in the observed E and B modes across the sky.

Contribution

The paper presents a novel, stable algorithm for identifying unpolarized points and applies it to detect non-Gaussianity in Planck polarization data at various scales.

Findings

Strong deviations from Gaussianity in E and B modes

Detection of non-Gaussian foreground contributions

Analysis across different angular scales

Abstract

We present a detailed test for Gaussianity of Planck polarization data using statistics of unpolarized points on the sky, i.e. such points where the linear polarization vanishes. The algorithm we propose for finding such points is stable and guarantees their 100% detection. Our approach allows us to analyze the data for Gaussianity of the signal at different angular scales and detect areas on the polarization maps with a significant contribution from unremoved non-Gaussian foregrounds. We found very strong deviations from Gaussianity for E and B modes in the observational data both over the entire sky and in some specific regions of the celestial sphere.