Detailed study of HWP non-idealities and their impact on future measurements of CMB polarization anisotropies from space

We study the propagation of a specific class of instrumental systematics to the reconstruction of the B-mode power spectrum of the cosmic microwave background (CMB). We focus on the non-idealities of the half-wave plate (HWP), a polarization modulator that is to be deployed by future CMB experiments, such as the phase-A satellite mission LiteBIRD. We study the effects of non-ideal HWP properties, such as transmittance, phase shift, and cross-polarization. To this end, we developed a simple, yet stand-alone end-to-end simulation pipeline adapted to LiteBIRD. We analyzed the effects of a possible mismatch between the measured frequency profiles of HWP properties (used in the mapmaking stage of the pipeline) and the actual profiles (used in the sky-scanning step). We simulated single-frequency, CMB-only observations to emphasize the effects of non-idealities on the BB power spectrum. We also considered multi-frequency observations to account for the frequency dependence of HWP properties and the contribution of foreground emission. We quantified the systematic effects in terms of a bias Delta r on the tensor-to-scalar ratio, r, with respect to the ideal case without systematic effects. We derived the accuracy requirements on the measurements of HWP properties by requiring Delta r < 10(-5) (1% of the expected LiteBIRD sensitivity on r). Our analysis is introduced by a detailed presentation of the mathematical formalism employed in this work, including the use of the Jones and Mueller matrix representations.

Automated summary

This study investigates the impact of a specific class of instrumental systematics on the reconstruction of the B-mode power spectrum of the cosmic microwave background (CMB). The focus is on the non-ideal properties of the half-wave plate (HWP), which is a polarization modulator used in future CMB experiments. The effects of non-ideal HWP properties, such as transmittance, phase shift, and cross-polarization, are studied using a simulation pipeline adapted to the LiteBIRD mission. The systematic effects on the tensor-to-scalar ratio are quantified, and accuracy requirements for the measurements of HWP properties are derived.