Predictions of Cosmic Microwave Background Foreground Dust Polarization Using Velocity Gradients

Observations of fluctuations in the cosmic microwave background provide information about primordial inhomogeneities in the universe. However, the B-mode polarization of the inflationary gravitational wave is contaminated by the Galactic foreground polarized radiation arising from dust aligned by interstellar magnetic fields. To trace magnetic fields, we use the Velocity Gradient Technique (VGT), which employs modern understanding of the nature of magnetohydrodynamic turbulent motions. In this paper, we combine the VGT with Principal Component Analysis (PCA) to improve the accuracy of magnetic field tracing. We apply the VGT-PCA to the high-resolution neutral hydrogen data from the GALFA-H i survey to predict the polarization of dust. We report that the predicted directions of dust polarization provide good correspondence with those reported by Planck 353 GHz, with the alignment measure between the two 0.79 0.01. We show that our results statistically agree with the Planck polarization in terms of magnetic field tracing. We find that the variation of dust emission efficiency across the sky is small. Using our maps of predicted polarization, we calculate the ratio of the E- and B-modes, and show that BB/EE 0.53 0.10, which is similar to the result from Planck polarization.