J/MNRAS/495/2607 IGMF limits with LOFAR (O'Sullivan+, 2020) ================================================================================ New constraints on the magnetization of the cosmic web using LOFAR Faraday rotation observations. O'Sullivan S.P., Bruggen M., Vazza F., Carretti E., Locatelli N.T., Stuardi C., Vacca V., Vernstrom T., Heald G., Horellou C., Shimwell T.W., Hardcastle M.J., Tasse C., Rottgering H. =2020MNRAS.495.2607O (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Active gal. nuclei ; Radio sources ; Polarization Keywords: techniques: polarimetric - galaxies: active - galaxies: magnetic fields - large scale structure of Universe - radio continuum: galaxies 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 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 <1.9rad/m^2^ (~95 per cent confidence). We use this limit with a simple model of an inhomogeneous universe to place an upper limit of 4nG on the cosmological co-moving magnetic field strength on Mpc scales. We also compare the RM data with a more realistic suite of cosmological magnetohydrodynamical 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 <0.5nG cannot be rejected by the current data; while stronger primordial fields or models with dynamo amplification in filaments are disfavoured. Description: Faraday rotation measure (RM) data for 349 pairs of radio source components with angular separations between 0.33 and 20-arcmin. The data presented here were obtained using the LOFAR Two-Metre Sky Survey (LoTSS), with a frequency range of 120 to 168MHz and a spectral resolution of 97.6kHz, between May 2014 and May 2020. The quoted RM errors are the nominal error calculated from the measurement noise and do not include systematic errors that would be relevant for comparison with other observations. The quoted RM errors are appropriate for the RM difference between close pairs, while for other applications we recommend adding a systematic uncertainty of approximately 0.05rad/m^2^. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 49 698 Coordinates, angular separation and RM values of all sources in the sample -------------------------------------------------------------------------------- See also: https://lofar-surveys.org : LOFAR Home Page Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 A4 --- ID RM pair identifier NNNp (1) 6- 7 I2 h RAh Right ascension (J2000) 9- 10 I2 min RAm Right ascension (J2000) 12- 16 F5.2 s RAs Right ascension (J2000) 18 A1 --- DE- Declination sign (J2000) 19- 20 I2 deg DEd Declination (J2000) 22- 23 I2 arcmin DEm Declination (J2000) 25- 29 F5.2 arcsec DEs Declination (J2000) 31- 35 F5.2 arcmin Sep Angular separation between pairs 37- 43 F7.3 rad/m2 RM Faraday rotation measure 45- 49 F5.3 rad/m2 e_RM Faraday rotation measure uncertainty (2) -------------------------------------------------------------------------------- Note (1): The ID column indicates classification as a random or physical pair with the r or p suffix. Note (2): The nominal RM error value does not include the error from the ionosphere RM correction, and thus is only valid in the case of taking the difference in RM between pairs in this catalogue. -------------------------------------------------------------------------------- Acknowledgements: Shane O'Sullivan, shane.osullivan(at)dcu.ie ================================================================================ (End) Patricia Vannier [CDS] 23-Jun-2022