CMB polarization map derived from the WMAP 5 year data through Harmonic Internal Linear Combination

TL;DR

This paper presents a new method called Harmonic Internal Linear Combination (HILC) to derive full-sky CMB polarization maps from WMAP 5-year data, improving foreground removal and enabling accurate power spectrum estimation.

Contribution

The paper introduces the HILC method that incorporates spatial variability of weights for better foreground reduction in polarization maps and derives an unbiased quadratic estimator for power spectrum analysis.

Findings

HILC maps produce TE and E mode spectra consistent with WMAP results.

HILC effectively reduces foreground contamination, especially at high resolution.

Method is suitable for future Planck polarization data analysis.

Abstract

We have derived whole-sky CMB polarization maps from the WMAP 5 year polarization data, using the Harmonic Internal Linear Combination (HILC) method. Our HILC method incorporates spatial variability of linear weights in a natural way and yields continuous linear weights over the entire sky. To estimate the power spectrum of HILC maps, we have derived a unbiased quadratic estimator, which is similar to the WMAP team's cross power estimator, but in a more convenient form for HILC maps. From our CMB polarization map, we have obtained TE correlation and E mode power spectra without applying any mask. They are similar to the WMAP team's estimation and consistent with the WMAP best-fit $\Lambda$CDM model. Foreground reduction by HILC method is more effective for high resolution and low noise data. Hence, our HILC method will enable effective foreground reduction in polarization data from the Planck surveyor.