Sensitive, high-resolution observations of Galactic neutral hydrogen (HI) reveal an intricate network of slender linear features. Across the high Galactic latitude sky, this HI is aligned with the magnetic field as traced by both starlight polarization and Planck 353 GHz polarized dust emission. The structure of the neutral interstellar medium is more tightly coupled to the magnetic field than previously known. At high Galactic latitudes, where the Planck data are noise-dominated, the HI data provide an independent constraint on the plane-of-sky magnetic field orientation, and hence the local dust polarization angle. The HI data thus provide a new tool for measuring foregrounds to polarized CMB experiments. I will discuss ongoing work using HI morphology to better constrain the polarized foreground, and to better understand the nature of the magnetized ISM.
Magnetic Fields in the Interstellar Medium
Susan Clark (IAS)
Thursday, 21 September 2017