MSc defense by Nadia Dachlythra – University of Copenhagen

MSc defense by Nadia Dachlythra

Statistical analysis of the CMB polarized data from 2018 Planck release

The collection of polarized data from the Cosmic Microwave Background (CMB) Radiation has set the ground for a new era in Cosmology. The Planck experiments are in the spotlight of the CMB research, since their first public release in 2013, as they have achieved CMB anisotropy measurements with unprecedented angular resolution and detector sensitivity. This thesis focuses on the investigation of some of the main statistical properties of the polarized data of Planck 2018 release. The analysis in question is highly important as the CMB polarization is the key to the detection of primordial gravitational waves. 

Initially, the polarization angle distribution is investigated in terms of uniformity and ways to correct the corresponding deviations. This results in the detection of peculiar Stokes parameters' monopoles and their further investigation. Additionally, a new universal method of E/B decomposition is proposed in order to 'by-pass' the coefficients of the known spin-weighted spherical harmonic decomposition for the polarization. Tests applied to the CMB maps reveal the accordance of the new and usual methods. Finally, a test of Q and U Gaussianity is conducted by employing the singular points of the polarization intensity field. The results are in good agreement with the theory when a flat-sky approximation is adopted along with strict choosing criteria of the unpolarized points. Monopole subtraction is, also in this case, a worth-imposing modification on the data.