Biases in Cosmic Microwave Background Secondary Anisotropies MeasurementsCai, Hongbo (2023) Biases in Cosmic Microwave Background Secondary Anisotropies Measurements. Doctoral Dissertation, University of Pittsburgh. (Unpublished)
AbstractThe development of Cosmic Microwave Background (CMB) experiments is leading to spectacular insights into understanding the universe through the measurements of CMB secondary anisotropies. In this thesis, we demonstrate topics in CMB secondary anisotropies and extracting science from them. In the first part of the thesis, we investigated the bias to the measurement of cosmic microwave background lensing (CMB lensing) power spectrum from the kinematic Sunyaev-Zel'dovich (kSZ) effect. We investigate for the first time the bias to CMB lensing reconstruction from temperature anisotropies due to the reionization-induced kSZ signal and show that it is negligible for both ongoing and upcoming experiments based on current numerical simulations of reionization. We also revisit the bias induced by the late-time kSZ field, using more recent kSZ simulations. In the second part of the thesis, we present a new publicly available code, \texttt{class\_rot}, which enables fast non-perturbative calculation of cosmic microwave background polarization power spectra due to both isotropic and anisotropic polarization rotation from cosmic birefringence. We describe the implementation of \texttt{class\_rot} in terms of both mathematical formalism and coding architecture. We also provide usage examples and demonstrate the accuracy of the code by comparing with simulations. In the third part of the thesis, we study how the presence of anisotropic cosmic birefringence impacts on lensing power spectrum measurements. We show that a scale-invariant cosmic birefringence with an amplitude of $A_{\rm CB}=10^{-7}$ can induce a $1-2\%$ bias to the measured lensing power spectrum for both CMB-S3-like and CMB-S4-like experiments. Our findings suggest that a birefringence signal well below our current limit can still bias the lensing measurements by around $10\%$ if unaccounted for. Cosmic birefringence, therefore, is potentially an important source of error to mitigate for the precision CMB lensing measurements in the future. Share
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