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

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.