Blind correction of the EB-leakage in the pixel domain

We study the problem of EB-leakage that is associated with incomplete polarized CMB sky. In the blind case that assumes no additional information about the statistical properties and amplitudes of the signal from the missing sky region, we prove that the recycling method (Liu et al.~2018) gives the unique best estimate of the EB-leakage. Compared to the previous method, this method reduces the uncertainties in the BB power spectrum due to EB-leakage by more than one order of magnitude in the most interesting domain of multipoles, where $\ell$ is between $80$ and $200$. This work also provides a useful guideline for observational design of future CMB experiments.Comment: Minor modification

Beam Prepared : Modeling optical systematics for current- and next-generation CMB experiments

The polarization of the Cosmic Microwave Background (CMB) is at the center of attention of the cosmological community, as the observable possibly offers a view of primordial gravitational waves. A signature from an early-universe gravitational wave background would be imprinted on the parity-odd pattern of the CMB polarization, namely the B-modes. Achieving a non-zero primordial B-mode detection would serve as indirect evidence of the current most favorable scenario describing the initial perturbations of the universe, referred to as cosmic inflation. Several current- and next-generation telescopes are targetting high-accuracy measurements of the polarized microwave sky, with a particular emphasis on probing the inflationary paradigm. This effort faces two key challenges. The first is the impact of the galactic contaminants on the cosmological signal, which may be tackled by telescopes with increased frequency and sky coverage. The second concern refers to systematic errors arising from the instrument itself, highlighting the necessity of establishing a robust framework for their modeling. This thesis focuses on the modeling of a leading category of systematics that is associated with the telescope’s optics in the context of CMB analysis. A part of the thesis discusses the impact that combining non-ideal beams with a specific type of realistic polarization modulators, namely Half-Wave-Plates (HWPs), has on the reconstructed CMB B-mode spectra of a simulated satellite experiment. The rest of the analysis refers to the Simons Observatory (SO) Small Aperture Telescopes (SATs) that are currently being deployed from the Atacama Desert in Chile. Specifically, I first assess our expected beam calibration capabilities during science observations of the SO SATs in terms of the telescope’s scientific objective. I then expand on the calibration strategy optimization and pipeline infrastructure I developed for the commissioning phase of the first deployed SAT. This study aimed to assess the telescope’s anticipated pointing and beam reconstruction accuracy during its initial observations. Finally, I investigate how natural variations in beam patterns across the SO observing frequency bands influence the large-scale B-mode spectra of the SATs.