The LOFAR LBA Sky Survey
Astronomy and Astrophysics, vol. 673, pp. A165
Abstract
Context. The Low Frequency Array (LOFAR) is the only existing radio interferometer able to observe at ultra-low frequencies (<100 MHz) with high resolution (<15") and high sensitivity (<1 mJy beam−1). To exploit these capabilities, the LOFAR Surveys Key Science Project is using the LOFAR Low Band Antenna (LBA) to carry out a sensitive wide-area survey at 41–66 MHz named the LOFAR LBA Sky Survey (LoLSS). Aims. LoLSS is covering the whole northern sky above declination 24° with a resolution of 15" and a sensitivity of 1–2 mJy beam−1 (1σ) depending on declination, field properties, and observing conditions. Here we present the first data release, including a discussion of the calibration strategy and the properties of the released images and catalogues. Methods. A fully automated pipeline was used to reduce the 95 fields included in this data release. The data reduction procedures developed for this project have a general application and are currently being used to process almost all LOFAR LBA interferometric observations. Compared to the preliminary release, direction-dependent errors have been derived and corrected for during the calibration process. This results in a typical sensitivity of 1.55 mJy beam−1, which is four times better than for the preliminary release, at the target resolution of 15". Results. The first data release of the LOFAR LBA Sky Survey covers 650 deg2 in the HETDEX spring field. The resultant data products released to the community include mosaic images (I and V Stokes) of the region, and a catalogue of 42 463 detected sources and related Gaussian components used to describe the sources' morphologies. Separate catalogues for the six in-band frequencies of 44, 48, 52, 56, 60, and 64 MHz are also released. Conclusions. The first data release of LoLSS shows that, despite the influences of the ionosphere and radio frequency interference, LOFAR can conduct large-scale surveys in the frequency window 42-66 MHz with unprecedentedly high sensitivity and resolution. The data can be used to derive unique information on the low-frequency spectral properties of many thousands of sources with a wide range of applications in extragalactic and galactic astronomy.
Authors 30
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Universität Hamburg · Istituto di Radioastronomia di Bologna
Affiliation as printed
Hamburger Sternwarte , Universität Hamburg , Gojenbergsweg 112 , 21029 Hamburg , Germany
INAF -Istituto di Radioastronomia , via P. Gobetti 101 , 40129 Bologna , Italy
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Affiliation as printed
Hamburger Sternwarte , Universität Hamburg , Gojenbergsweg 112 , 21029 Hamburg , Germany
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Leiden University · Leiden Observatory · Netherlands Institute for Radio Astronomy
Affiliation as printed
ASTRON , the Netherlands Institute for Radio Astronomy , Postbus 2 , 7990 AA Dwingeloo , The Netherlands
Leiden Observatory , Leiden University , PO Box 9513 , 2300 RA Leiden , The Netherlands
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Netherlands Institute for Radio Astronomy
Affiliation as printed
ASTRON , the Netherlands Institute for Radio Astronomy , Postbus 2 , 7990 AA Dwingeloo , The Netherlands
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Affiliation as printed
Hamburger Sternwarte , Universität Hamburg , Gojenbergsweg 112 , 21029 Hamburg , Germany
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Netherlands Institute for Radio Astronomy
Affiliation as printed
ASTRON , the Netherlands Institute for Radio Astronomy , Postbus 2 , 7990 AA Dwingeloo , The Netherlands
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Affiliation as printed
Centre for Astrophysics Research , University of Hertfordshire , College Lane , Hatfield AL10 9AB , UK
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Netherlands Institute for Radio Astronomy
Affiliation as printed
ASTRON , the Netherlands Institute for Radio Astronomy , Postbus 2 , 7990 AA Dwingeloo , The Netherlands
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Netherlands Institute for Radio Astronomy
Affiliation as printed
ASTRON , the Netherlands Institute for Radio Astronomy , Postbus 2 , 7990 AA Dwingeloo , The Netherlands
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Leiden University · Leiden Observatory · Netherlands Institute for Radio Astronomy
Affiliation as printed
ASTRON , the Netherlands Institute for Radio Astronomy , Postbus 2 , 7990 AA Dwingeloo , The Netherlands
Leiden Observatory , Leiden University , PO Box 9513 , 2300 RA Leiden , The Netherlands
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory , Leiden University , PO Box 9513 , 2300 RA Leiden , The Netherlands
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Centre National de la Recherche Scientifique · Observatoire de Paris · Galaxies, Etoiles, Physique et Instrumentation · Université Paris Diderot
Affiliation as printed
GEPI , Observatoire de Paris , CNRS , Université Paris-Diderot , 5 place Jules Janssen , 92190 Meudon , France
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Affiliation as printed
Ruhr University Bochum , Faculty of Physics and Astronomy , Astronomical Institute , Universitätsstr. 150 , 44801 Bochum , Germany
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Istituto di Radioastronomia di Bologna · University of Bologna
Affiliation as printed
DIFA -Universitá di Bologna , via Gobetti 93/2 , 40129 Bologna , Italy
INAF -Istituto di Radioastronomia , via P. Gobetti 101 , 40129 Bologna , Italy
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Istituto di Radioastronomia di Bologna · University of Bologna
Affiliation as printed
DIFA -Universitá di Bologna , via Gobetti 93/2 , 40129 Bologna , Italy
INAF -Istituto di Radioastronomia , via P. Gobetti 101 , 40129 Bologna , Italy
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Istituto di Radioastronomia di Bologna
Affiliation as printed
INAF -Istituto di Radioastronomia , via P. Gobetti 101 , 40129 Bologna , Italy
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Affiliation as printed
Astronomical Observatory of the Jagiellonian University , ul. Orla 171 , 30-244 Kraków , Poland
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Universität Hamburg · Istituto di Radioastronomia di Bologna
Affiliation as printed
Hamburger Sternwarte , Universität Hamburg , Gojenbergsweg 112 , 21029 Hamburg , Germany
INAF -Istituto di Radioastronomia , via P. Gobetti 101 , 40129 Bologna , Italy
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National Radio Astronomy Observatory
Affiliation as printed
National Radio Astronomy Observatory , 520 Edgemont Road , Charlottesville , VA 22903 , USA
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Leiden University · Leiden Observatory
Affiliation as printed
Leiden Observatory , Leiden University , PO Box 9513 , 2300 RA Leiden , The Netherlands
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Affiliation as printed
School of Physical Sciences , The Open University , Walton Hall , Milton Keynes MK7 6AA , UK
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Istituto di Radioastronomia di Bologna
Affiliation as printed
INAF -Istituto di Radioastronomia , via P. Gobetti 101 , 40129 Bologna , Italy
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Affiliation as printed
Fakultät für Physik , Universität Bielefeld , Postfach 100131 , 33501 Bielefeld , Germany
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Université d'Orléans · Centre National de la Recherche Scientifique · Observatoire de Paris · Laboratoire d’études spatiales et d’instrumentation en astrophysique · Laboratoire de Physique et Chimie de l’Environnement et de l’Espace
Affiliation as printed
LLESIA , CNRS -Observatoire de Paris , 5 Pl. Jules Janssen , 92190 Meudon , France
LPC2E , CNRS -Université d'Orléans , 3 Av. de la Recherche Scientifique , 45071 Orléans , France
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