Absolute polarization angle calibration using polarized diffuse Galactic emission observed by BICEP

Abstract

We present a method of cross-calibrating the polarization angle of a polarimeter using Bicep Galactic observations. Bicep was a ground based experiment using an array of 49 pairs of polarization sensitive bolometers observing from the geographic South Pole at 100 and 150 GHz. The Bicep polarimeter is calibrated to ±0.01 in cross-polarization and less than ±0.7◦ in absolute polarization orientation. Bicep observed the temperature and polarization of the Galactic plane (R.A = 100◦ ∼ 270◦ and Dec. = −67◦ ∼ −48◦). We show that the statistical error in the 100 GHz Bicep Galaxy map can constrain the polarization angle offset of Wmap W band to 0.6◦ ± 1.4◦. The expected 1σ errors on the polarization angle cross-calibration for Planck or EPIC are 1.3◦ and 0.3◦ at 100 and 150 GHz, respectively. We also discuss the expected improvement of the Bicep Galactic field observations with forthcoming Bicep2 and Keck observations.