Polarized point sources in the LOFAR Two-meter Sky Survey: A preliminary catalog
Reviewartikel, 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.

ISM: magnetic fields



C.L. Van Eck

Radboud Universiteit

M. Haverkorn

Radboud Universiteit

M.I.R. Alves

Radboud Universiteit

R. Beck


P.N. Best

University of Edinburgh

E. Carretti

Istituto nazionale di astrofisica (INAF)

K. Chyzy

Uniwersytet Jagiellonski w Krakowie

J.S. Farnes

Radboud Universiteit

K. Ferriere

Université de Toulouse

M. J. Hardcastle

University of Hertfordshire

G. Heald

Rijksuniversiteit Groningen

Commonwealth Scientific and Industrial Research Organisation (CSIRO)

Cathy Horellou

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

M. Iacobelli

Netherlands Institute for Radio Astronomy (ASTRON)

V. Jelic

Ruđer Bošković Institutet

D.D. Mulcahy

University of Manchester

S. O'Sullivan

Universität Hamburg

I.M. Polderman

Radboud Universiteit

Wolfgang Reich


C. J. Riseley

Commonwealth Scientific and Industrial Research Organisation (CSIRO)

H.J.A. Rottgering

Universiteit Leiden

D.H.F.M. Schnitzeler


T. W. Shimwell

Netherlands Institute for Radio Astronomy (ASTRON)

Universiteit Leiden

V. Vacca

Istituto nazionale di astrofisica (INAF)

J. Vink

Universiteit Van Amsterdam

G. J. White


Open University

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 613 A58


Subatomär fysik

Astronomi, astrofysik och kosmologi

Annan fysik


Grundläggande vetenskaper



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