Predictions of Cosmic Microwave Background Foregrounds Dust Polarization Using Velocity Gradients

TL;DR

This paper presents a novel method combining Velocity Gradient Technique and PCA to accurately predict dust polarization in the cosmic microwave background, aiding in the separation of primordial signals from galactic foregrounds.

Contribution

It introduces an improved magnetic field tracing method using VGT combined with PCA applied to HI data, enhancing dust polarization prediction accuracy.

Findings

Predicted dust polarization directions closely match Planck observations (AM=0.79).

The method's polarization predictions statistically agree with Planck data.

Calculated BB/EE ratio of 0.53 aligns with Planck results.

Abstract

The 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, which employs a modern understanding of the nature of magneto-hydrodynamics turbulent motions. In this paper, we combine the VGT with the 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-HI survey to predict the polarization of dust. We report that the predicted directions of dust polarization provide good correspondence with those reported by Planck 353GHz, the alignment measure between the two AM=0.79. 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, which is similar to the result from Plank polarization.