CARRETTI, ETTOREETTORECARRETTIVACCA, VALENTINAVALENTINAVACCAO'Sullivan, S. P.S. P.O'SullivanHeald, G. H.G. H.HealdHorellou, C.C.HorellouRöttgering, H. J. A.H. J. A.RöttgeringScaife, A. M. M.A. M. M.ScaifeShimwell, T. W.T. W.ShimwellShulevski, A.A.ShulevskiStuardi, C.C.StuardiVernstrom, T.T.Vernstrom2022-09-272022-09-2720220035-8711http://hdl.handle.net/20.500.12386/32652We used the rotation measure (RM) catalogue derived from the LOFAR Two-metre Sky Survey Data Release 2 (LoTSS DR2) at 144 MHz to measure the evolution with redshift of the extragalactic RM (RRM: Residual RM) and the polarization fraction (p) of sources in low-density environments. We also measured the same at 1.4 GHz by cross-matching with the NRAO VLA Sky Survey RM catalogue. We find that RRM versus redshift is flat at 144 MHz, but, once redshift-corrected, it shows evolution at high significance. Also, p evolves with redshift with a decrement by a factor of ~8 at z ~ 2. Comparing the 144-MHz and 1.4-GHz data, we find that the observed RRM and p are most likely to have an origin local to the source at 1.4 GHz, while a cosmic web filament origin is favoured at 144 MHz. If we attribute the entire signal to filaments, we infer a mean rest-frame RRM per filament of RRM$_{\rm 0,f} = 0.71 \pm 0.07 \, \, \rm rad\, m^{-2}$ and a magnetic field per filament of B<SUB>f</SUB> = 32 ± 3 nG. This is in agreement with estimates obtained with a complementary method based on synchrotron emission stacking, and with cosmological simulations if primordial magnetic fields are amplified by astrophysical source field seeding. The measurement of an RRM<SUB>0, f</SUB> supports the presence of diffuse baryonic gas in filaments. We also estimated a conservative upper limit of the filament magnetic turbulence of $\sigma _{\rm RRM_{\rm 0,f}} =0.039 \pm 0.001 \, \, \rm rad\, m^{-2}$, concluding that the ordered magnetic field component dominates in filaments.STAMPAenArticle10.1093/mnras/stac3842-s2.0-85127957750http://arxiv.org/abs/2202.04607v1https://academic.oup.com/mnras/article-abstract/512/1/945/6528375?redirectedFrom=fulltext2022MNRAS.512..945CFIS/05 - ASTRONOMIA E ASTROFISICA