Limiting Magnetic Fields in the Cosmic Web with Diffuse Radio Emission
  We set limits on the presence of the synchrotron cosmic web through the
cross-correlation of the 2.3 GHz S-PASS survey with a model of the local cosmic
web derived from constrained magnetohydrodynamic (MHD) simulations. The MHD
simulation assumes cosmologically seeded magnetic fields amplified during
large-scale structure formation, and a population of relativistic
electrons/positrons from proton-proton collisions within the intergalactic
medium. We set a model-dependent 3$\sigma$ upper limit on the synchrotron
surface brightness of 0.16 mJy arcmin$^{-2}$ at 2.3 GHz in filaments.
Extrapolating from magnetic field maps created from the simulation, we infer an
upper limit (density-weighted) magnetic field of 0.03 (0.13) $\mu$G in
filaments at the current epoch, and a limit on the primordial magnetic field
(PMF) of B$_{PMF}$~1.0 nG.
