Author(s): , , ,
Institution(s): 1. Columbia University, 2. Space Telescope Science Institute
The Planck all-sky polarization maps provide key foreground information for studies of the polarized CMB, including the search for primordial B-mode polarization. However, the Planck 353 GHz polarization measurements lack the sensitivity at high latitudes to precisely describe the polarized dust foregrounds. We present the discovery that the orientation of neutral hydrogen (HI) structures traces the Planck 353 GHz polarization angle with surprising precision across a range of angular scales. This result demonstrates a deep connection between the structure of diffuse Galactic HI and Galactic dust. When combined with Planck 353 GHz data or other measures of dust polarization amplitude, this method will enable higher fidelity maps for foreground subtraction. As it is particularly powerful at high latitudes, this method may be the best tool yet developed for identifying the cleanest regions of high-latitude sky for CMB polarization experiments to target.