Detailed study of HWP non-idealities and their impact on future measurements of CMB polarization anisotropies from space
S. Giardiello, M. Gerbino, L. Pagano, J. Errard, A. Gruppuso, H. Ishino, M. Lattanzi, P. Natoli, G. Patanchon, F. Piacentini, G. Pisano
Abstract
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 Δ 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 Δ 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.