- Broida 3302
- Special Astrophysics Colloquium
Magnetic fields thread our Milky Way Galaxy, influencing interstellar physics from cosmic ray propagation to star formation. The magnetic interstellar medium is also a formidable foreground for experimental cosmology, particularly for the quest to find signatures of inflation in the polarized cosmic microwave background. Despite its importance across scientific realms, the structure of the Galactic magnetic field is not well understood. Observational tracers like polarized dust emission yield only sky-projected, distance-integrated measurements of the three-dimensional magnetic structure. I will discuss new ways to probe interstellar magnetism in three dimensions, by combining high-resolution observations of Galactic neutral hydrogen with recent insights into how gas morphology encodes properties of the ambient magnetic field. The next decade of cosmology will generate deep observations of foreground synchrotron and polarized dust emission. I will present a vision for harnessing these and other data to map the Galactic magnetic field, elucidate its origin and role in astrophysical processes, and separate the Galactic signal from the universe beyond.