Institute for Advanced Study Astrophysics Seminar

Observations of fluctuations in the CMB provide information about primordial inhomogeneities in the universe. However, the B-mode polarization of the inflationary gravitational wave is contaminated by the Galactic dust and synchrotron foreground polarization, arising from the complicated Galactic  magnetic fields (GMFs).  In this talk, I will present new approaches to modeling the Galactic foregrounds and GMFs by leveraging the anisotropic properties of MHD turbulence and nonlinear spectroscopic mapping effects. Specifically, I will introduce the velocity gradient technique and a machine-learning-based framework that utilize 21 cm neutral hydrogen emission to infer the 3D orientation and total strength of the GMF. By incorporating the Galactic rotation curve, these methods further reconstruct the full 3D spatial distribution of the GMF. I will compare these results with stellar polarization data and Planck 353 GHz polarization observations, highlighting the advantages and implications of these techniques for CMB foreground mitigation.