Volume 613, May 2018
|Number of page(s)||18|
|Section||Catalogs and data|
|Published online||01 June 2018|
Polarized point sources in the LOFAR Two-meter Sky Survey: A preliminary catalog
Department of Astrophysics/IMAPP, Radboud University,
PO Box 9010,
Nijmegen, The Netherlands
2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
3 SUPA, Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
4 INAF-Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius, CA, Italy
5 Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30-244 Kraków, Poland
6 IRAP, Université de Toulouse, CNRS, 9 avenue du Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
7 Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
8 CSIRO Astronomy and Space Science, 26 Dick Perry Ave, Kensington, WA 6151, Australia
9 University of Groningen, Kapteyn Astronomical Institute, 9700 AV Groningen, The Netherlands
10 Dept of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
11 ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands
12 Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
13 Jodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
14 Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
15 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
16 Bendenweg 51, 53121 Bonn, Germany
17 Astronomical Institute Anton Pannekoek, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
18 RAL Space, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK
19 Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
Accepted: 9 January 2018
The polarization properties of radio sources at very low frequencies (<200 MHz) have not been widely measured, but the new generation of low-frequency radio telescopes, including the Low Frequency Array (LOFAR: a Square Kilometre Array Low pathfinder), now gives us the opportunity to investigate these properties. In this paper, we report on the preliminary development of a data reduction pipeline to carry out polarization processing and Faraday tomography for data from the LOFAR Two-meter Sky Survey (LOTSS) and present the results of this pipeline from the LOTSS preliminary data release region (10h45m–15h30m right ascension, 45°–57° declination, 570 square degrees). We have produced a catalog of 92 polarized radio sources at 150 MHz at 4.′3 resolution and 1 mJy rms sensitivity, which is the largest catalog of polarized sources at such low frequencies. We estimate a lower limit to the polarized source surface density at 150 MHz, with our resolution and sensitivity, of 1 source per 6.2 square degrees. We find that our Faraday depth measurements are in agreement with previous measurements and have significantly smaller errors. Most of our sources show significant depolarization compared to 1.4 GHz, but there is a small population of sources with low depolarization indicating that their polarized emission is highly localized in Faraday depth. We predict that an extension of this work to the full LOTSS data would detect at least 3400 polarized sources using the same methods, and probably considerably more with improved data processing.
Key words: polarization / ISM: magnetic fields
© ESO 2018
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.