Biases in Cosmic Microwave Background Secondary Anisotropies Measurements

Abstract: The development of Cosmic Microwave Background (CMB) experiments is leading to spectacular insights into understanding the universe through CMB secondary anisotropies measurements. In this thesis,  I will present topics in CMB secondary anisotropies and the biases to their measurements. Firstly, I will demonstrate the bias to the measurement of cosmic microwave background lensing (CMB lensing) power spectrum from the reionization kinematic Sunyaev-Zel'dovich (kSZ) effect and show that it is negligible for both ongoing and upcoming experiments based on current numerical simulations of reionization.  I will also revisit the bias induced by the late-time kSZ field, using more recent kSZ simulations. Secondly, I will present a new publicly available code Class_rot, which enables fast non-perturbative calculation of cosmic microwave background polarization power spectra due to the polarization rotation from cosmic birefringence. I will provide usage examples and demonstrate the accuracy of the code by comparing with simulations. Finally, I will demonstrate how the presence of anisotropic cosmic birefringence impacts on lensing power spectrum measurements. The results suggest that a birefringence signal well below our current limit can still bias the lensing measurements by around 10% if unaccounted for.