The LOFAR Two-metre Sky Survey

We present the third data release of the LOFAR Two-metre Sky Survey (LoTSS-DR3). The survey images cover 88% of the northern sky and were created from 12 950 h of data (18.6 PB) accumulated over 10.5 years. Producing the images took 20 million core hours of processing through direction-independent and direction-dependent calibration pipelines that correct for instrumental effects as well as spatially and temporally varying ionospheric distortions. In our 120–168 MHz continuum mosaic images with an angular resolution of 6″ (9″ below declination 10°) we catalogue 13 667 877 sources, formed from 16 943 656 Gaussian components. The scatter in the astrometric precision approximately follows the expected noise-like behaviour but with an additional systematic component of at least 0.24″ that is likely due to calibration imperfections. The random flux density scale error is 6%, while the systematic offset was previously shown to be within 2%. The median sensitivity of our mosaics is 92 μJy beam −1 , improving to 68 μJy beam −1 at high observing elevations, but degrading to 183 μJy beam −1 at the celestial equator due to station area projection effects. Completeness simulations, accounting for realistic source models, time- and bandwidth-smearing effects, and astrometric errors, indicate that we detect more than 95% of compact sources with integrated flux densities exceeding 9 times the local root mean square (RMS) noise. However, the recovered source counts in a particular integrated flux density bin do not match the injected counts until flux densities exceed 45 times the local RMS noise. The Euclidean-normalised differential source counts derived from the survey constrain the radio source population over five orders of magnitude and are in good agreement with previous deep and wide-area surveys. All data products are publicly available, including catalogues, individual-field Stokes I , Q , U , and V images, mosaicked Stokes I images, and uv data with associated direction-dependent calibration solutions.

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Journal
Astronomy and Astrophysics
Published
2026-02-05
DOI
https://doi.org/10.1051/0004-6361/202557749
Primary Topic
Radio Astronomy Observations and Technology
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article
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article

The LOFAR Two-metre Sky Survey

J. R. Callingham, DJ Bomans, S.P. O'Sullivan, D. Schwarz et al.
Astronomy and Astrophysics
Radio Astronomy Observations and Technology
article

The LOFAR Two-metre Sky Survey

J. R. Callingham, DJ Bomans, S.P. O'Sullivan, D. Schwarz, H.K. Vedantham, B. Rusholme, KJ Kawabata Duncan, J.E. Conway, G. White, DG Nair, H.W. Edler, I.D. Roberts, R.J. van Weeren, J.M.G.H.J. de Jong, L.K. Morabito, D.J.B. Smith, C. Manzano, A. Miskolczi, N. Jackson, M. Brentjens, M. Haverkorn, C. Groeneveld, M. Stein, V. Cuciti, S. ter Veen, M. Mevius, R. Kondapally, R. Cassano, J.C.S. Pierce, K. T. Chyży, S Camera, D. Dallacasa, A. Shulevski, S.J. Nakoneczny, M. Loose, G.K. Miley, A. Ahmadi, E. Orru, W.L. Williams, F. Sweijen, I. Prandoni, M. Jamrozy, D. Rafferty, B. Mingo, A. Botteon, C. Tasse, C. Stuardi, C.L. Hale, J.M. Boxelaar, T. W. Shimwell, L. Böhme, M. Hoeft, D.N. Hoang, M.J. Jarvis, M. Kunert-Bajraszewska, V. Heesen, G. Gürkan, J.P. McKean, R. Timmerman, J. Moldón, M. Magliocchetti, M. Bilicki, T. Pasini, L. Alegre, E. Bonnassieux, K. Rajpurohit, K. Małek, V. Jelic, A. Drabent, S. Sethi, A. Bonafede, M. Iacobelli, J. Petley, B. Asabere, M. Brüggen, M. Arias, M. Pashapour-Ahmadabadi, G. Di Gennaro, G. Brunetti, M. Bonato, J. Chilufya, M. Cianfaglione, B. Bahr-Kalus, E. De Rubeis, M. Kadler, C.J. Riseley, F. De Gasperin, M.A. Horton, P.N. Best, M. Hajduk, R. Morganti, R.J. Dettmar, M. Vaccari, S. Wijnholds, M. Brienza, H. Holties, B. Barkus, A. Misra, C. Horellou, M. J. Hardcastle, J.H. Croston, P. Dabhade
article en

Abstract

We present the third data release of the LOFAR Two-metre Sky Survey (LoTSS-DR3). The survey images cover 88% of the northern sky and were created from 12 950 h of data (18.6 PB) accumulated over 10.5 years. Producing the images took 20 million core hours of processing through direction-independent and direction-dependent calibration pipelines that correct for instrumental effects as well as spatially and temporally varying ionospheric distortions. In our 120–168 MHz continuum mosaic images with an angular resolution of 6″ (9″ below declination 10°) we catalogue 13 667 877 sources, formed from 16 943 656 Gaussian components. The scatter in the astrometric precision approximately follows the expected noise-like behaviour but with an additional systematic component of at least 0.24″ that is likely due to calibration imperfections. The random flux density scale error is 6%, while the systematic offset was previously shown to be within 2%. The median sensitivity of our mosaics is 92 μJy beam −1 , improving to 68 μJy beam −1 at high observing elevations, but degrading to 183 μJy beam −1 at the celestial equator due to station area projection effects. Completeness simulations, accounting for realistic source models, time- and bandwidth-smearing effects, and astrometric errors, indicate that we detect more than 95% of compact sources with integrated flux densities exceeding 9 times the local root mean square (RMS) noise. However, the recovered source counts in a particular integrated flux density bin do not match the injected counts until flux densities exceed 45 times the local RMS noise. The Euclidean-normalised differential source counts derived from the survey constrain the radio source population over five orders of magnitude and are in good agreement with previous deep and wide-area surveys. All data products are publicly available, including catalogues, individual-field Stokes I , Q , U , and V images, mosaicked Stokes I images, and uv data with associated direction-dependent calibration solutions.

Astronomy and AstrophysicsVol. 707
Universidad Complutense de Madrid (ES), Leiden University (NL), Jagiellonian University (PL), Rutherford Appleton Laboratory (GB), Centre National de la Recherche Scientifique (FR), University of Hertfordshire (GB), Radboud University Nijmegen (NL), Université de Bordeaux (FR), University of Waterloo (CA), Universität Hamburg (DE), University of Groningen (NL), Forschungszentrum Jülich (DE), University of Concepción (CL), Durham University (GB), Bielefeld University (DE), The Open University (GB), University of Cambridge (GB), Université Paris Sciences et Lettres (FR), Observatoire de Paris (FR), Center for Theoretical Physics (PL), University of Oxford (GB), Osservatorio astronomico di Bologna (IT), National Centre for Nuclear Research (PL), Laboratoire d'Astrophysique de Bordeaux (FR), Istituto Nazionale di Fisica Nucleare, Sezione di Torino (IT), Max Planck Institute for Astrophysics (DE), Osservatorio Astrofisico di Torino (IT), Royal Observatory (GB), SKA Observatory (GB), Istituto di Radioastronomia di Bologna (IT), South African Radio Astronomy Observatory (ZA), Institute of Astronomy (RU), Ruđer Bošković Institute (HR), Center for Astrophysics Harvard & Smithsonian (US), Astronomical Institute of the Slovak Academy of Sciences (SK), Astronomy and Space (AU), Thüringer Landessternwarte Tautenburg (DE), Astronomical Observatory (RS), Max Planck Institute for Radio Astronomy (DE), Instituto de Astrofísica de Andalucía (ES), University of Warmia and Mazury in Olsztyn (PL), UK Astronomy Technology Centre (GB), University of Turin (IT), Chalmers University of Technology (SE), Ss. Cyril and Methodius University in Skopje (MK), University of the Western Cape (ZA), National Institute for Astrophysics (IT), University of Amsterdam (NL), Ruhr University Bochum (DE), Netherlands Institute for Radio Astronomy (NL), University of Bologna (IT), Polish Academy of Sciences (PL)
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