New constraints on the magnetization of the cosmic web using LOFAR Faraday rotation observations
Journal article, 2020

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 Delta RM along the line of sight between non-physical pairs. From our analysis, we find no significant difference between the ?RM distributions of the physical and non-physical pairs, limiting the excess Faraday rotation contribution to <1.9 rad/m(2) (similar to 95% confidence). We use this limit with a simple model of an inhomogeneous universe to place an upper limit of 4 nG on the cosmological co-moving magnetic field strength on Mpc scales. We also compare the RM data with a more realistic 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 magnetic field strengths <0.5 nG cannot be rejected by the current data; while stronger primordial fields or models with dynamo amplification in filaments are disfavoured.

galaxies: active

radio continuum: galaxies

large:scale structure of Universe

galaxies: magnetic fields

techniques: polarirnetnc

Author

S. P. O'Sullivan

Dublin City University

University of Hamburg

M. Bruggen

University of Hamburg

F. Vazza

University of Hamburg

Istituto nazionale di astrofisica (INAF)

University of Bologna

E. Carretti

Istituto nazionale di astrofisica (INAF)

N. Locatelli

University of Bologna

Istituto nazionale di astrofisica (INAF)

C. Stuardi

Istituto nazionale di astrofisica (INAF)

University of Bologna

V. Vacca

Istituto nazionale di astrofisica (INAF)

T. Vernstrom

Commonwealth Scientific and Industrial Research Organisation (CSIRO)

G. Heald

Commonwealth Scientific and Industrial Research Organisation (CSIRO)

Cathy Horellou

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

T. W. Shimwell

Netherlands Institute for Radio Astronomy (ASTRON)

Leiden University

M. J. Hardcastle

University of Hertfordshire

C. Tasse

Université Paris PSL

H. Rottgering

Leiden University

Monthly Notices of the Royal Astronomical Society

0035-8711 (ISSN) 1365-2966 (eISSN)

Vol. 495 3 2607-2619

Subject Categories

Astronomy, Astrophysics and Cosmology

Other Physics Topics

Fusion, Plasma and Space Physics

DOI

10.1093/mnras/staa1395

More information

Latest update

10/10/2023