Simple Foreground Cleaning Algorithm For Detecting Primordial B-Mode Polarization Of The Cosmic Microwave Background
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We reconsider the pixel-based, "template" polarized foreground removal method within the context of a next-generation, low-noise, low-resolution (0 degrees.5 FWHM) space-borne experiment measuring the cosmological B-mode polarization signal in the cosmic microwave background (CMB). This method was first applied to polarized data by the Wilkinson Microwave Anisotropy Probe (WMAP) team and further studied by Efstathiou et al. We need at least three frequency channels: one is used for extracting the CMB signal, whereas the other two are used to estimate the spatial distribution of the polarized dust and synchrotron emission. No extra data from non-CMB experiments or models are used. We extract the tensor-to-scalar ratio (r) from simulated sky maps outside the standard polarization mask (P06) of WMAP consisting of CMB, noise (2 mu K arcmin), and a foreground model, and find that, even for the simplest three-frequency configuration with 60, 100, and 240 GHz, the residual bias in r is as small as Delta r approximate to 0.002. This bias is dominated by the residual synchrotron emission due to spatial variations of the synchrotron spectral index. With an extended mask with f(sky) = 0.5, the bias is reduced further down to <0.001.