Testing CMB Anomalies in E-mode Polarization with Current and Future Data

Several large scale anomalous features have been noticed in the cosmic microwave background (CMB) temperature anisotropy measurements, but the constraints on anomaly statistics are hard to improve because the instrumental noise is already smaller than the cosmic variance. In this work, we explored the power of the CMB polarization (E-mode) data to corroborate four anomalies in CMB temperature data: the lack of large angular-scale correlations, the alignment of the quadrupole and octupole (Q-O), the preference for odd-parity modes, and the hemispherical power asymmetry. We used CMB simulations with noise representative of three experiments — the Planck satellite, the Cosmology Large Angular Scale Surveyor (CLASS), and the LiteBIRD satellite — to test how current and future data constrain the anomalies. We found the correlation coefficients ρ between temperature and E-mode estimators to be less than 0.1, except for the odd-parity mode preference (ρ=0.17 for cosmic-variance-limited), confirming that E-modes provide a check on the anomalies that is largely independent of temperature data. Compared to Planck component-separated CMB data (SMICA), the putative LiteBIRD survey would reduce errors on E-mode anomaly estimators by factors of ~3 for preference of odd-parity modes and hemispherical power asymmetry, ~26 (1.5) for lack of large-scale correlation. The improvement on Q-O alignment is not obvious due to large cosmic variance, but we found the ability to pin down the estimator value will be improved by a factor >100. Improvements with CLASS are intermediate to these.