dc.contributor.author O'Sullivan, S. P. dc.contributor.author Brüggen, M. dc.contributor.author Vazza, F. dc.contributor.author Carretti, E. dc.contributor.author Locatelli, N. dc.contributor.author Stuardi, C. dc.contributor.author Vacca, V. dc.contributor.author Vernstrom, T. dc.contributor.author Heald, G. dc.contributor.author Horellou, C. dc.contributor.author Shimwell, T. W. dc.contributor.author Hardcastle, M. J. dc.contributor.author Tasse, C. dc.contributor.author Röttgering, H. dc.date.accessioned 2020-08-05T00:08:36Z dc.date.available 2020-08-05T00:08:36Z dc.date.issued 2020-07-01 dc.identifier.citation O'Sullivan , S P , Brüggen , M , Vazza , F , Carretti , E , Locatelli , N , Stuardi , C , Vacca , V , Vernstrom , T , Heald , G , Horellou , C , Shimwell , T W , Hardcastle , M J , Tasse , C & Röttgering , H 2020 , ' New constraints on the magnetization of the cosmic web using LOFAR Faraday rotation observations ' , Monthly Notices of the Royal Astronomical Society , vol. 495 , no. 3 , staa1395 , pp. 2607–2619 . https://doi.org/10.1093/mnras/staa1395 dc.identifier.issn 0035-8711 dc.identifier.other PURE: 19694324 dc.identifier.other PURE UUID: ce2b22ea-d622-43ab-8d18-59cc1c796f11 dc.identifier.other ArXiv: http://arxiv.org/abs/2002.06924v1 dc.identifier.uri http://hdl.handle.net/2299/23032 dc.description This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society, Volume 495, Issue 3, July 2020, Pages 2607–2619: © 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. dc.description.abstract Measuring the properties of extragalactic magnetic fields through the effect of Faraday rotation provides a means to understand the origin and evolution of cosmic magnetism. Here we use data from the LOFAR Two-Metre Sky Survey (LoTSS) to calculate the Faraday rotation measure (RM) of close pairs of extragalactic radio sources. By considering the RM difference ($\Delta$RM) between physical pairs (e.g. double-lobed radio galaxies) and non-physical pairs (i.e. close projected sources on the sky), we statistically isolate the contribution of extragalactic magnetic fields to the total RM variance along the line of sight. We find a difference in the rms of $\Delta$RM between non-physical and physical pairs of 0.4$\pm$0.3 rad/m$^2$, and a difference in the corresponding median |$\Delta$RM| values of 0.3$\pm$0.4 rad/m$^2$. This enables us to place an upper limit on the co-moving cosmological magnetic field strength of $B <2.5$ nG on Mpc scales. This limit is obtained by exploring a wide range of input magnetic field strengths in a model of cosmic over-densities that realistically reflects the observed matter inhomogeneities on large scales. We also compare the LOFAR RM data with a suite of cosmological MHD simulations, that explore different magnetogenesis scenarios. Both magnetization of the large scale structure by astrophysical processes such as galactic and AGN outflows, and simple primordial scenarios with seed field strengths of $B\lesssim0.5$ nG cannot be rejected by the current data, while stronger primordial fields or models with dynamo amplification in filaments are disfavoured. In general, LOFAR polarized sources are typically located in regions of the Universe with low RM variance, making them excellent probes of the weak magnetization of cosmic filaments and voids far from galaxy cluster environments. en dc.format.extent 13 dc.language.iso eng dc.relation.ispartof Monthly Notices of the Royal Astronomical Society dc.subject astro-ph.CO dc.subject astro-ph.GA dc.title New constraints on the magnetization of the cosmic web using LOFAR Faraday rotation observations en dc.contributor.institution Centre for Astrophysics Research dc.contributor.institution School of Physics, Astronomy and Mathematics dc.description.status Peer reviewed rioxxterms.version VoR rioxxterms.versionofrecord https://doi.org/10.1093/mnras/staa1395 rioxxterms.type Journal Article/Review herts.preservation.rarelyaccessed true
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