Issue |
A&A
Volume 648, April 2021
The LOFAR Two Meter Sky Survey
|
|
---|---|---|
Article Number | A1 | |
Number of page(s) | 18 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361/202038804 | |
Published online | 07 April 2021 |
The LOFAR Two-meter Sky Survey: Deep Fields Data Release 1
I. Direction-dependent calibration and imaging
1
GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen,
92190 Meudon, France
e-mail: cyril.tasse@obspm.fr
2
Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University, Grahamstown 6140, South Africa
3
USN, Observatoire de Paris, CNRS, PSL, UO, Nançay, France
4
ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD, Dwingeloo, The Netherlands
5
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
6
Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
7
School of Physical Sciences and Centre for Astrophysics & Relativity, Dublin City University,
Glasnevin, D09 W6Y4, Ireland
8
SUPA, Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK
9
South African Radio Astronomy Observatory, Observatory 7925, Cape Town, South Africa
10
European Southern Observatory, Karl-Schwarzchild-Strasse 2, 85748 Garching bei München, Germany
11
Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
12
Centre for Extragalactic Astronomy, Department of Physics, Durham University, Durham, DH1 3LE, UK
13
INAF – Istituto di Radioastronomia, Via P. Gobetti 101, 40129 Bologna, Italy
14
INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122, Padova, Italy
15
Italian ALMA Regional Centre, Via Gobetti 101, 40129 Bologna, Italy
16
Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30-244 Kraków, Poland
17
Jodrell Bank Centre for Astrophysics, University of Manchester, Alan Turing Building, Oxford Road, M13 9PL, UK
18
CSIRO Astronomy and Space Science, PO Box 1130, Bentley WA 6102, Australia
19
Astrophysics, Department of Physics, Keble Road, Oxford, OX1 3RH, UK
20
Department of Physics & Astronomy, University of the Western Cape, Private Bag X17, Bellville, Cape Town 7535, South Africa
21
Institute of Sensors, Signals and Systems, Heriot-Watt University, Edinburgh EH14 4AS, UK
22
Astrophysics & Cosmology Research Unit, School of Mathematics, Statistics & Computer Science, University of KwaZulu-Natal, Durban 3690, South Africa
23
Fakultät für Physik, Universität Bielefeld, Postfach 100131, 33501 Bielefeld, Germany
24
Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam, The Netherlands
Received:
1
July
2020
Accepted:
10
November
2020
The Low Frequency Array (LOFAR) is an ideal instrument to conduct deep extragalactic surveys. It has a large field of view and is sensitive to large-scale and compact emission. It is, however, very challenging to synthesize thermal noise limited maps at full resolution, mainly because of the complexity of the low-frequency sky and the direction dependent effects (phased array beams and ionosphere). In this first paper of a series, we present a new calibration and imaging pipeline that aims at producing high fidelity, high dynamic range images with LOFAR High Band Antenna data, while being computationally efficient and robust against the absorption of unmodeled radio emission. We apply this calibration and imaging strategy to synthesize deep images of the Boötes and Lockman Hole fields at ~150 MHz, totaling ~80 and ~100 h of integration, respectively, and reaching unprecedented noise levels at these low frequencies of ≲30 and ≲23 μJy beam−1 in the inner ~3 deg2. This approach is also being used to reduce the LOTSS-wide data for the second data release.
Key words: techniques: interferometric / techniques: image processing / surveys / galaxies: active / galaxies: starburst / radio continuum: galaxies
© C. Tasse et al. 2021
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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