Testing Cosmic Microwave Background Anomalies in E-mode Polarization with Current and Future Data

Abstract

In this paper, we explore the power of the cosmic microwave background (CMB) polarization (E-mode) data to corroborate four potential anomalies in CMB temperature data: the lack of large angular-scale correlations, the alignment of the quadrupole and octupole (Q–O), the point-parity asymmetry, and the hemispherical power asymmetry. We use 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 find the correlation coefficients ρ between temperature and E-mode estimators to be less than 0.1, except for the point-parity asymmetry (ρ = 0.17 for cosmic-variance-limited simulations), 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 hemispherical power asymmetry and point-parity asymmetry, and by ∼26 for lack of large-scale correlation. The improvement in 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.

Unraveling the CMB lack-of-correlation anomaly with the cosmological gravitational wave background

“…Although this provides an unbiased estimate of the spectra, it does not minimize their variance. For this reason, it would be interesting to explore this anomaly with an analogous analysis employing some maximum likelihood estimator, which instead allows one to get a minimal variance estimate of the spectra [47,105,106]. We leave this for future work.…”

“…In fact, CMB temperature has been observed in a cosmic variance-limited fashion on low and intermediate multipole scales; thus, we cannot unveil any new information from the temperature alone. To determine whether these are the consequence of a physical phenomenon, we must exploit other observables, correlated with the CMB temperature, such as the CMB polarization [43][44][45][46][47][48].…”

CLASS Data Pipeline and Maps for 40 GHz Observations through 2022

“…While the search for tensor perturbations has progressed at ℓ  30 led by Keck/ Keck Collaboration et al (2021), the largest-scale B modes would provide the distinctive "reionization peak" feature and would be most unambiguously separable from the late-time lensing effect (Zaldarriaga & Seljak 1998). The largest angular scales also provide access to beyond-the-standard-model physics (e.g., Muir et al 2018;Hogan 2019;Hogan et al 2023;Shi et al 2023) and the physics of the interstellar medium (e.g., Caldwell et al 2017). It is the goal of the Cosmology Large Angular Scale Surveyor (CLASS) project to develop the technology and techniques needed to explore the large-scale CMB polarization from the ground.…”