Constraint on magnetized galactic outflows from LOFAR rotation measure data

Outflows from galaxies that are driven by active galactic nuclei and star formation activity spread magnetic fields into the intergalactic medium. The importance of this process can be assessed using cosmological magnetohydrodynamical numerical modeling of the baryonic feedback on the large-scale structure, such as that of IllustrisTNG simulations. We use the Faraday rotation measure data of the LOFAR Two-Metre Sky Survey (LoTSS) to test the IllustrisTNG baryonic feedback model. We show that the IllustrisTNG overpredicts the root mean square of the residual rotation measure in LoTSS, which suggests that pollution of the intergalactic medium by magnetized outflows from galaxies is less important than the estimate from IllustrisTNG. This fact supports the hypothesis that the volume-filling large-scale magnetic fields in voids of the large-scale structure are of cosmological origin.