Exploring two-spin internal linear combinations for the recovery of the CMB polarization

Abstract

We present a methodology to recover cosmic microwave background (CMB) polarization in which the quantity $P=Q+iU$ is linearly combined at different frequencies using complex coefficients. This is the most general linear combination of the $Q$ and $U$ Stokes parameters which preserves the physical coherence of the residual contribution on the CMB estimation. The approach is applied to the internal linear combination (ILC) and the internal template fitting (ITF) methodologies. The variance of $P$ of the resulting map is minimized to compute the coefficients of the linear combination. One of the key aspects of this procedure is that it serves to account for a global frequency-dependent shift of the polarization phase. Although in the standard case, in which no global E-B transference depending on frequency is expected in the foreground components, minimizing $⟨|P{|}^2⟩$ is similar to minimizing $⟨Q^2⟩$ and $⟨U^2⟩$ separately (as previous methodologies proceed), multiplying $Q$ and $U$ by different coefficients induces arbitrary changes in the polarization angle and it does not preserve the coherence between the spinorial components. The approach is tested on simulations, obtaining a similar residual level with respect to the one obtained with other implementations of the ILC, and perceiving the polarization rotation of a toy model with the frequency dependence of the Faraday rotation.

14 pages, 8 figures, 2 tables. Accepted for publication in MNRAS

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Cited by in corpus (11)

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• Exploring Cosmic Origins with CORE: B-mode Component Separation
• Multi-Clustering Needlet-ILC for CMB B-modes component separation
• Spin-SILC: CMB polarisation component separation with spin wavelets
• Analysis of NILC performance on B-modes data of sub-orbital experiments
• Efficient ILC analysis on polarization maps after EB leakage correction
• Recovering Cosmic Microwave Background Polarization Signals with Machine Learning
• Foreground removal with ILC methods for AliCPT-1
• Delensing for Precision Cosmology: Optimizing Future CMB B-mode Surveys to Constrain r
• A new approach of estimating the Galactic thermal dust and synchrotron polarized emission template in the microwave bands
• Polarization angle requirements for CMB B-mode experiments. Application to the LiteBIRD satellite