Modeling of Galactic Foreground Polarization with Velocity Gradients

TL;DR

This paper demonstrates that the Velocity Gradient Technique (VGT) effectively traces the galactic magnetic field, aligning well with Planck and stellar polarization data, aiding in foreground removal for primordial B-mode detection.

Contribution

The study applies VGT to distinguish velocity clouds and confirms its effectiveness in constructing 3D galactic magnetic fields, advancing foreground modeling techniques.

Findings

VGT aligns well with Planck polarization data.

VGT effectively distinguishes different velocity clouds.

VGT enhances 3D magnetic field modeling.

Abstract

The detection of primordial B-mode polarization is still challenging due to the relatively low amplitude compared to the galactic foregrounds. To remove the contribution from the foreground, a comprehensive picture of the galactic magnetic field is indispensable. The Velocity Gradient Technique (VGT) is promising in tracing magnetic fields based on the modern understanding of the magneto-hydrodynamic turbulence. In this work, we apply VGT to a HI region containing an intermediate velocity cloud and a local velocity cloud, which are distinguishable in position-position-velocity space. We show that VGT gives an excellent agreement with the Planck polarization and stellar polarization. We confirm the advantages of VGT in constructing the 3D galactic magnetic field.