CMB polarization map derived from the WMAP 5 year data through the harmonic internal linear combination method

Abstract

We have derived whole-sky cosmic microwave background 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 an 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 cosmic microwave background 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 $\ensuremath{\Lambda}\mathrm{CDM}$ model. Foreground reduction by the 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.