Speaker: Tom Weisgarber (Chicago)
- Voids: <1nG; filaments: ~0.3 µG; galaxies: ~1 µG; clusters: 10 µG. No detections of B-fields in voids.
- Gamma rays interact with the extragalactic background light (EBL) and create electron-positron pairs, which then cascade down to create more gamma rays. This cascade is then observed with some opening angle. Pair production and inverse Compton scattering are the important processes in creating the cascades.
- Semi-analytic model for the cascade: Huan+ (2011, ApJL 735, 28). Using the blazar RGB J0710+591, they constrain the B-field to be <3e-16 G (<3e-18 G for a 3 year livetime).