@article{330deda3447249fdbf19713cf35c6728,
title = "The Faraday Rotation Measure Grid of the LOFAR Two-metre Sky Survey: Data Release 2",
abstract = "A Faraday rotation measure (RM) catalogue, or RM Grid, is a valuable resource for the study of cosmic magnetism. Using the second data release (DR2) from the LOFAR Two-metre Sky Survey (LoTSS), we have produced a catalogue of 2461 extragalactic high-precision RM values across 5720 deg2 of sky (corresponding to a polarized source areal number density of ∼0.43 deg-2). The linear polarization and RM properties were derived using RM synthesis from the Stokes Q and U channel images at an angular resolution of 20 arcsec across a frequency range of 120 to 168 MHz with a channel bandwidth of 97.6 kHz. The fraction of total intensity sources (>1 mJy beam-1) found to be polarized was ∼0.2 per cent. The median detection threshold was 0.6 mJy beam-1 (8σQU), with a median RM uncertainty of 0.06 rad m-2 (although a systematic uncertainty of up to 0.3 rad m-2 is possible, after the ionosphere RM correction). The median degree of polarization of the detected sources is 1.8 per cent, with a range of 0.05 per cent to 31 per cent. Comparisons with cm-wavelength RMs indicate minimal amounts of Faraday complexity in the LoTSS detections, making them ideal sources for RM Grid studies. Host galaxy identifications were obtained for 88 per cent of the sources, along with redshifts for 79 per cent (both photometric and spectroscopic), with the median redshift being 0.6. The focus of the current catalogue was on reliability rather than completeness, and we expect future versions of the LoTSS RM Grid to have a higher areal number density. In addition, 25 pulsars were identified, mainly through their high degrees of linear polarization.",
keywords = "catalogues, galaxies: active, magnetic fields, polarization, radio continuum: galaxies, techniques: polarimetric",
author = "O'Sullivan, {S. P.} and Shimwell, {T. W.} and Hardcastle, {M. J.} and C. Tasse and G. Heald and E. Carretti and M. Br{\"u}ggen and V. Vacca and C. Sobey and {Van Eck}, {C. L.} and C. Horellou and R. Beck and M. Bilicki and S. Bourke and A. Botteon and Croston, {J. H.} and A. Drabent and K. Duncan and V. Heesen and S. Ideguchi and M. Kirwan and L. Lawlor and B. Mingo and B. Nikiel-Wroczy{\'n}ski and J. Piotrowska and Scaife, {A. M.M.} and {Van Weeren}, {R. J.}",
note = "Funding Information: SPO and MB acknowledge financial support from the Deutsche Forschungsgemeinschaft (DFG) under grant BR2026/23. MB ac- knowledges support from the Deutsche Forschungsgemeinschaft under Germany's Excellence Strategy - EXC 2121 'Quantum Universe' -390833306. AMS gratefully acknowledges support from an Alan Turing Institute AI Fellowship EP/V030302/1. KJD acknowledges funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska- Curie grant agreement No. 892117 (HIZRAD). MJH acknowl- edges support from the UK STFC [ST/V000624/1]. JHC and BM acknowledge support from the UK Science and Technol- ogy Facilities Council (STFC) under grants ST/R000794/1, and ST/T000295/1 MB is supported by the Polish National Science Cen- ter through grants no. 2020/38/E/ST9/00395, 2018/30/E/ST9/00698, 2018/31/G/ST9/03388, and 2020/39/B/ST9/03494, and by the Polish Ministry of Science and Higher Education through grant DIR/WK/2018/12. VV acknowledges support from INAF mainstream project 'Galaxy Clusters Science with LOFAR' 1.05.01.86.05. BNW acknowledges support from the Polish National Science Centre (NCN), grant no. UMO-2016/23/D/ST9/00386. The authors of the Polish scientific institutions thank the Ministry of Science and Higher Education (MSHE), Poland for grant- ing funds for the Polish contribution to the ILT (MSHE deci- sion no. DIR/WK/2016/2017/05-1) and for maintenance of the LOF AR LOF AR PL-611 Lazy, LOF AR PL-612 Baldy stations (MSHE decisions: no. 46/E-383/SPUB/SP/2019 and no. 59/E- 383/SPUB/SP/2019.1, respecti vely). AD ackno wledges support by the BMBF Verbundforschung under the grant 05A20STA. RJvW acknowledges support from the VIDI research programme with project number 639.042.729, which is financed by the Netherlands Organisation for Scientific Research (NWO). This research made use of ASTROPY, a community-developed core PYTHON package for astronomy (Astropy Collaboration 2013 ) hosted at http://www.astrop y.org/, of MATPLOTLIB (Hunter 2007 ), of APLPY (Robitaille & Bressert 2012 ), an open-source astronomical plotting package for python hosted at http:// aplpy.github.com/, and of TOPCAT, an interactive graphical viewer and editor for tabular data (Taylor 2005 ). This research has made use of 'Aladin sky atlas' developed at CDS, Strasbourg Observatory, France (Bonnarel et al. 2000 ). LOFAR (van Haarlem et al. 2013 ) is the Low Frequency Array designed and constructed by ASTRON. It has observing, data processing, and data storage facilities in several countries, which are owned by various parties (each with their own funding sources), and that are collectively operated by the ILT foundation under a joint scientific polic y. The ILT resources hav e benefited from the following recent major funding sources: CNRS-INSU, Observatoire de Paris and Universit{\'e} d'Orl{\'e}ans, France; BMBF, MIWF-NRW, MPG, Germany; Science Foundation Ireland (SFI), Department of Business, En- terprise and Innovation (DBEI), Ireland; NWO, The Netherlands; The Science and Technology Facilities Council, UK; Ministry of Science and Higher Education, Poland; The Istituto Nazionale di Astrofisica (INAF), Italy. This research made use of the Dutch national e-infrastructure with support of the SURF Cooperative (e- infra 180169) and the LOFAR e-infra group. The J{\"u}lich LOFAR Long Term Archive and the German LOFAR network are both coordinated and operated by J{\"u}lich Supercomputing Centre (JSC), and computing resources on the supercomputer JUWELS at JSC were provided by the Gauss Centre for Supercomputing e.V. (grant CHTB00) through the John von Neumann Institute for Computing (NIC). This research made use of the University of Hertfordshire high-performance computing facility and the LOFAR-UK computing facility located at the University of Hertfordshire and supported by STFC [ST/P000096/1], and of the Italian LOFAR IT computing infrastructure supported and operated by INAF, and by the Physics Department of Turin university (under an agreement with Consorzio Interuniversitario per la Fisica Spaziale) at the C3S Supercomputing Centre, Italy. The authors thank the referee for comments which impro v ed the paper. Publisher Copyright: {\textcopyright} 2022 The Author(s).",
year = "2023",
month = mar,
day = "1",
doi = "10.1093/mnras/stac3820",
language = "English",
volume = "519",
pages = "5723--5742",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "4",
}