The Faraday Rotation Measure Grid of the LOFAR Two-metre Sky Survey: Data Release 2
Journal article, 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.
radio continuum: galaxies
magnetic fields
catalogues
techniques: polarimetric
polarization
galaxies: active
Author
S. P. O'Sullivan
Dublin City University
T. W. Shimwell
Netherlands Institute for Radio Astronomy (ASTRON)
Leiden University
M. J. Hardcastle
University of Hertfordshire
C. Tasse
Rhodes University
Université Paris PSL
G. Heald
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
E. Carretti
Istituto nazionale di astrofisica (INAF)
M. Bruggen
University of Hamburg
V. Vacca
Istituto nazionale di astrofisica (INAF)
C. Sobey
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
C. L. Van Eck
University of Toronto
Cathy Horellou
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
R. Beck
Max Planck Society
M. Bilicki
Polish Academy of Sciences
Stephen Bourke
Chalmers, Space, Earth and Environment, Onsala Space Observatory
A. Botteon
Leiden University
J. H. Croston
Open University
A. Drabent
Thüringer Landessternwarte Tautenburg
K. Duncan
Royal Observatory
V Heesen
University of 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
Jagiellonian University in Kraków
J. Piotrowska
Jagiellonian University in Kraków
A. M. M. Scaife
Alan Turing Institute
University of Manchester
R. J. van Weeren
Leiden University
Monthly Notices of the Royal Astronomical Society
0035-8711 (ISSN) 1365-2966 (eISSN)
Vol. 519 4 5723-5742Subject Categories
Accelerator Physics and Instrumentation
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
DOI
10.1093/mnras/stac3820