I’ve just submitted to MNRAS my newest project conducted as part of the S-band All Sky Polarization Survey (S-PASS) project. We’ve taken the 2.3 GHz total intensity (just radio brightness) map of the southern sky provided by S-PASS and performed a cross-correlation with a model of the cosmic-web (obtained from a constrained magnetohydrodynamic simulation of the local Universe, see below) in order to set an upper limit on the cosmological magnetic fields in filaments of B>0.03 G (B>0.13 G if you take a density weighted average). As a side note, we were also able to infer an upper limit on the primordial magnetic field of B> 1.0 nG! This limit is better than that obtained by Planck, and on par with the recent combined Planck + South Pole Telescope limit, though it’s highly model dependent. An advance peak can be found here (paper). An image (from the paper) of the model radio emission is shown below, and the simulations where done by Klaus Dolag.