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V-LoTSS: The circularly polarised LOFAR Two-metre Sky Survey

Callingham, J.R.; Shimwell, T.W.; Vedantham, H.K.; Bassa, C.G.; O’Sullivan, S.P.; Yiu, T.W.H.; Bloot, S.; Best, P.N.; Hardcastle, M.J.; Haverkorn, M.; Kavanagh, R.D.; Lamy, L.; Pope, B.J.S.; Röttgering, H.J.A.; Schwarz, D.J.; Tasse, C.; van Weeren, R.J.; White, G.J.; Zarka, P.; Bomans, D.J.; Bonafede, A.; Bonato, M.; Botteon, A.; Bruggen, M.; Chyży, K.T.; Drabent, A.; Emig, K.L.; Gloudemans, A.J.; Gürkan, G.; Hajduk, M.; Hoang, D.N.; Hoeft, M.; Iacobelli, M.; Kadler, M.; Kunert-Bajraszewska, M.; Mingo, B.; Morabito, L.K.; Nair, D.G.; Pérez-Torres, M.; Ray, T.P.; Riseley, C.J.; Rowlinson, A.; Shulevski, A.; Sweijen, F.; Timmerman, R.; Vaccari, M.; Zheng, J.

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J.R. Callingham

T.W. Shimwell

H.K. Vedantham

C.G. Bassa

S.P. O’Sullivan

T.W.H. Yiu

S. Bloot

P.N. Best

M.J. Hardcastle

M. Haverkorn

R.D. Kavanagh

L. Lamy

B.J.S. Pope

H.J.A. Röttgering

D.J. Schwarz

C. Tasse

R.J. van Weeren

G.J. White

P. Zarka

D.J. Bomans

A. Bonafede

M. Bonato

A. Botteon

M. Bruggen

K.T. Chyży

A. Drabent

K.L. Emig

A.J. Gloudemans

G. Gürkan

M. Hajduk

D.N. Hoang

M. Hoeft

M. Iacobelli

M. Kadler

M. Kunert-Bajraszewska

B. Mingo

D.G. Nair

M. Pérez-Torres

T.P. Ray

C.J. Riseley

A. Rowlinson

A. Shulevski

F. Sweijen

R. Timmerman

M. Vaccari

J. Zheng


We present the detection of 68 sources from the most sensitive radio survey in circular polarisation conducted to date. We used the second data release of the 144 MHz LOFAR Two-metre Sky Survey to produce circularly polarised maps with a median noise of 140 µJy beam−1 and resolution of 20″ for ≈27% of the northern sky (5634 deg2). The leakage of total intensity into circular polarisation is measured to be ≈0.06%, and our survey is complete at flux densities ≥1 mJy. A detection is considered reliable when the circularly polarised fraction exceeds 1%. We find the population of circularly polarised sources is composed of four distinct classes: stellar systems, pulsars, active galactic nuclei, and sources unidentified in the literature. The stellar systems can be further separated into chromospherically active stars, M dwarfs, and brown dwarfs. Based on the circularly polarised fraction and lack of an optical counterpart, we show it is possible to infer whether the unidentified sources are likely unknown pulsars or brown dwarfs. By the completion of this survey of the northern sky, we expect to detect 300±100 circularly polarised sources.


Callingham, J., Shimwell, T., Vedantham, H., Bassa, C., O’Sullivan, S., Yiu, T., …Zheng, J. (2023). V-LoTSS: The circularly polarised LOFAR Two-metre Sky Survey. Astronomy & Astrophysics, 670, Article A124.

Journal Article Type Article
Acceptance Date Dec 17, 2022
Online Publication Date Feb 17, 2023
Publication Date 2023-02
Deposit Date Jun 7, 2023
Publicly Available Date Jun 21, 2023
Journal Astronomy & Astrophysics
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 670
Article Number A124


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