The LOFAR Two-metre Sky Survey I. Survey description and preliminary data release*

T. W. Shimwell (1) , H.J.A. Röttgering (1) , P P Best (2) , W.L. Williams (3) , J.T Dijkema (4) , F. de Gasperin (5) , D N Hoang (1) , M. J. Hardcastle (6) , H H Heald (4) , A A Horneffer (7) , H Intema (1) , E.K. Mahony (4) , S. Mandal (1) , A.P. Mechev (1) , M M Morabito (1) , J J B Oonk (4) , D R Rafferty (8) , E. Retana-Montenegro (1) , J S Sabater (2) , C Tasse (9) , R. J. van Weeren (10) , M M Brüggen (8) , G. Brunetti (11) , K. T. Chyzy (12) , J E Conway (13) , M M Haverkorn (14) , N. Jackson (15) , M. J. Jarvis (16) , J P Mckean (4) , G.K. Miley (1) , R. Morganti (4) , G.J. White (17) , M M Wise (18) , I van Bemmel (4) , R R Beck (7) , M. Brienza (4) , A A Bonafede (8) , G. Calistro Rivera (1) , R. Cassano (11) , A A Clarke (15) , D D Cseh (19) , A A Deller (4) , A A Drabent (20) , W van Driel (21, 9) , D Engels (5) , H Falcke (22) , C Ferrari (23) , S S Fröhlich (24) , M.A. Garrett (4) , J. Harwood (4) , V. Heesen (25) , M M Hoeft (26) , C H Horellou (27) , F P Israël (1) , A. D. Kapińska (28) , M. Kunert-Bajraszewska (29) , D.J. Mckay (30) , N.R. Mohan (31) , E O Orrú (4) , R. F. Pizzo (4) , P P Prandoni (11) , D.J. Schwarz (32) , A A Shulevski (4) , M S Sipior (4) , D.J.B Smith (6) , S S Sridhar (4) , M S Steinmetz (33) , A. Stroe (34) , E E Varenius (13) , P. P. van Der Werf (1) , J A Zensus (7) , J. T. L. Zwart (35)

1 Leiden Observatory [Leiden]
2 IfA - Institute for Astronomy [Edinburgh]
3 Centre for Astrophysics Research
4 ASTRON - Netherlands Institute for Radio Astronomy
5 Hamburger Sternwarte/Hamburg Observatory
6 UH - University of Hertfordshire [Hatfield]
7 MPIFR - Max-Planck-Institut für Radioastronomie
8 UHH - Universität Hamburg
9 GEPI - Galaxies, Etoiles, Physique, Instrumentation
10 CfA - Harvard-Smithsonian Center for Astrophysics
11 IRA - Istituto di Radioastronomia [Bologna]
12 Astronomical Observatory [Kraków]
13 OSO - Onsala Space Observatory
14 Radboud University [Nijmegen]
15 Jodrell Bank Centre for Astrophysics
16 Oxford Astrophysics
17 Department of Physics and Astronomy [Milton Keynes]
18 AI PANNEKOEK - Astronomical Institute Anton Pannekoek
19 AIM (UMR7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
20 TLS - Thüringer Landessternwarte Tautenburg
21 USN - Unité Scientifique de la Station de Nançay
22 IMAPP - Institute for Mathematics, Astrophysics and Particle Physics
23 LAGRANGE - Joseph Louis LAGRANGE
24 RUB - Ruhr University Bochum = Ruhr-Universität Bochum
25 School of Physics and Astronomy [Southampton]
26 JIVE ERIC - Joint Institute for VLBI in Europe
27 Department of Earth and Space Sciences [Göteborg]
28 UWA - The University of Western Australia
29 TCfA - Torun Centre for Astronomy
30 University of Oulu
31 NCRA - National Centre for Radio Astrophysics [Pune]
32 Universität Bielefeld
33 AIP - Leibniz-Institut für Astrophysik Potsdam
34 ESO - European Southern Observatory
35 UWC - University of the Western Cape

The LOFAR Two-metre Sky Survey (LoTSS) is a deep 120–168 MHz imaging survey that will eventually cover the entire northern sky. Each of the 3170 pointings will be observed for 8 h, which, at most declinations, is sufficient to produce ∼5 resolution images with a sensitivity of ∼100 µJy/beam and accomplish the main scientific aims of the survey, which are to explore the formation and evolution of massive black holes, galaxies, clusters of galaxies and large-scale structure. Owing to the compact core and long baselines of LOFAR, the images provide excellent sensitivity to both highly extended and compact emission. For legacy value, the data are archived at high spectral and time resolution to facilitate subarcsecond imaging and spectral line studies. In this paper we provide an overview of the LoTSS. We outline the survey strategy, the observational status, the current calibration techniques, a preliminary data release, and the anticipated scientific impact. The preliminary images that we have released were created using a fully automated but direction-independent calibration strategy and are significantly more sensitive than those produced by any existing large-area low-frequency survey. In excess of 44 000 sources are detected in the images that have a resolution of 25 , typical noise levels of less than 0.5 mJy/beam, and cover an area of over 350 square degrees in the region of the HETDEX Spring Field (right ascension 10h45m00s to 15h30m00s and declination 45 • 00 00 to 57 • 00 00).

Mots clés: surveys – catalogs – radio continuum: general – techniques: image processing; surveys – catalogs – radio continuum: general – techniques: image processing

Domaines: Astrophysique [astro-ph]

T. W. Shimwell, H.J.A. Röttgering, P P Best, W.L. Williams, J.T Dijkema, et al.. The LOFAR Two-metre Sky Survey I. Survey description and preliminary data release*. Astronomy and Astrophysics - A&A, 2017, 598, A104 (22 p.). ⟨10.1051/0004-6361/201629313⟩. ⟨insu-01521308⟩