The Faraday Rotation Measure Grid of the LOFAR Two-metre Sky Survey: Data Release 2
Artikel i vetenskaplig tidskrift, 2023

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 deg(2) of sky (corresponding to a polarized source areal number density of similar to 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 similar to 0.2 percent. The median detection threshold was 0.6 mJy beam(-1) (8 sigma(QU)), with a median RM uncertainty of 0.06 rad m(-2) (although a systematic uncertainty of up to 0.3 radm(-2) is possible, after the ionosphere RM correction). The median degree of polarization of the detected sources is 1.8 percent, with a range of 0.05 percent to 31 percent. 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 percent of the sources, along with redshifts for 79 percent (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.


techniques: polarimetric

magnetic fields


galaxies: active

radio continuum: galaxies


S. P. O'Sullivan

Dublin City University

T. W. Shimwell

Universiteit Leiden

Netherlands Institute for Radio Astronomy (ASTRON)

M. J. Hardcastle

University of Hertfordshire

C. Tasse

Rhodes University

Université de recherche Paris Sciences et Lettres

G. Heald

CSIRO Astronomy and Space Science

E. Carretti

Istituto nazionale di astrofisica (INAF)

M. Bruggen

Universität Hamburg

V. Vacca

INAF Osservatorio Astronomico di Cagliari

C. Sobey

CSIRO Astronomy and Space Science

C. L. Van Eck

University of Toronto

Cathy Horellou

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

R. Beck


M. Bilicki

Polish Academy of Sciences

Stephen Bourke

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium

A. Botteon

Universiteit Leiden

J. H. Croston

Open University

A. Drabent

Thüringer Landessternwarte Tautenburg

K. Duncan

Royal Observatory

V Heesen

Universität Hamburg

S. Ideguchi

National Astronomical Observatory of Japan

M. Kirwan

Dublin City University

L. Lawlor

Dublin City University

B. Mingo

Open University

B. Nikiel-Wroczynski

Uniwersytet Jagiellonski w Krakowie

J. Piotrowska

Uniwersytet Jagiellonski w Krakowie

A. M. M. Scaife

Alan Turing Institute

University of Manchester

R. J. van Weeren

Universiteit Leiden

Monthly Notices of the Royal Astronomical Society

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

Vol. 519 4 5723-5742


Acceleratorfysik och instrumentering

Astronomi, astrofysik och kosmologi

Atom- och molekylfysik och optik



Mer information

Senast uppdaterat