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

TL;DR

This paper introduces a method to calibrate the polarization angle of CMB experiments using Galactic emission observed by BICEP, achieving high precision and informing future calibration efforts for Planck and EPIC.

Contribution

The paper presents a novel cross-calibration technique for polarization angles using Galactic emission data from BICEP, improving calibration accuracy for CMB polarization measurements.

Findings

BICEP's polarization angle calibration accuracy is within 0.7 degrees.

Galactic observations constrain WMAP's polarization angle offset to 0.6 ± 1.4 degrees.

Projected calibration errors for Planck and EPIC are 1.3 and 0.3 degrees, respectively.

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 degrees in absolute polarization orientation. BICEP observed the temperature and polarization of the Galactic plane (R.A= 100 degrees ~ 270 degrees and Dec. = -67 degrees ~ -48 degrees). We show that the statistical error in the 100 GHz BICEP Galaxy map can constrain the polarization angle offset of WMAP Wband to 0.6 degrees +\- 1.4 degrees. The expected 1 sigma errors on the polarization angle cross-calibration for Planck or EPIC are 1.3 degrees and 0.3 degrees at 100 and 150 GHz, respectively. We also discuss the expected improvement of the BICEP Galactic field observations with forthcoming BICEP2 and Keck observations.