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LOFAR facet calibration

LOFAR facet calibration
LOFAR facet calibration
LOFAR, the Low-Frequency Array, is a powerful new radio telescope operating between 10 and 240 MHz. LOFAR allows detailed sensitive high-resolution studies of the low-frequency radio sky. At the same time LOFAR also provides excellent short baseline coverage to map diffuse extended emission. However, producing high-quality deep images is challenging due to the presence of direction-dependent calibration errors, caused by imperfect knowledge of the station beam shapes and the ionosphere. Furthermore, the large data volume and presence of station clock errors present additional difficulties. In this paper we present a new calibration scheme, which we name facet calibration, to obtain deep high-resolution LOFAR High Band Antenna images using the Dutch part of the array. This scheme solves and corrects the direction-dependent errors in a number of facets that cover the observed field of view. Facet calibration provides close to thermal noise limited images for a typical 8 hr observing run at ~ 5" resolution, meeting the specifications of the LOFAR Tier-1 northern survey.
0067-0049
1-16
van Weeren, R.J.
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Williams, W.L.
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Hardcastle, M.J.
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Heald, G.
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de Gasperin, F.
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Miley, G.K.
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Cassano, R.
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Ferrari, C.
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Hoeft, M.
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Jarvis, M.J.
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Intema, H.T.
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Murray, S.S.
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Orrú, E.
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Pizzo, R.
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Simionescu, A.
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Stroe, A.
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van der Tol, S.
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White, G.J.
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van Weeren, R.J.
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Williams, W.L.
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Hardcastle, M.J.
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Shimwell, T.W.
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Rafferty, D.A.
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Sabater, J.
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Heald, G.
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Sridhar, S.S.
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Dijkema, T.J.
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Brunetti, G.
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Brüggen, M.
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Andrade-Santos, F.
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Dawson, W.A.
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Bîrzan, L.
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Cassano, R.
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Chyży, K.T.
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Croston, J.H.
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Ensslin, T.
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Ferrari, C.
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Hoeft, M.
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Horellou, C.
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Jarvis, M.J.
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Kraft, R.P.
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Mevius, M.
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Intema, H.T.
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Murray, S.S.
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Orrú, E.
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Pizzo, R.
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Simionescu, A.
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Stroe, A.
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van der Tol, S.
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White, G.J.
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van Weeren, R.J., Williams, W.L. and Hardcastle, M.J. et al. (2016) LOFAR facet calibration. The Astrophysical Journal Supplement Series, 223 (2), 1-16. (doi:10.3847/0067-0049/223/1/2).

Record type: Article

Abstract

LOFAR, the Low-Frequency Array, is a powerful new radio telescope operating between 10 and 240 MHz. LOFAR allows detailed sensitive high-resolution studies of the low-frequency radio sky. At the same time LOFAR also provides excellent short baseline coverage to map diffuse extended emission. However, producing high-quality deep images is challenging due to the presence of direction-dependent calibration errors, caused by imperfect knowledge of the station beam shapes and the ionosphere. Furthermore, the large data volume and presence of station clock errors present additional difficulties. In this paper we present a new calibration scheme, which we name facet calibration, to obtain deep high-resolution LOFAR High Band Antenna images using the Dutch part of the array. This scheme solves and corrects the direction-dependent errors in a number of facets that cover the observed field of view. Facet calibration provides close to thermal noise limited images for a typical 8 hr observing run at ~ 5" resolution, meeting the specifications of the LOFAR Tier-1 northern survey.

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Accepted/In Press date: 18 January 2016
e-pub ahead of print date: 7 March 2016
Published date: 7 March 2016
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 401970
URI: http://eprints.soton.ac.uk/id/eprint/401970
ISSN: 0067-0049
PURE UUID: e793065f-ee86-4740-a327-05aee9f09655

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Date deposited: 26 Oct 2016 10:59
Last modified: 16 Dec 2019 19:39

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Contributors

Author: R.J. van Weeren
Author: W.L. Williams
Author: M.J. Hardcastle
Author: T.W. Shimwell
Author: D.A. Rafferty
Author: J. Sabater
Author: G. Heald
Author: S.S. Sridhar
Author: T.J. Dijkema
Author: G. Brunetti
Author: M. Brüggen
Author: F. Andrade-Santos
Author: G.A. Ogrean
Author: H.J.A. Röttgering
Author: W.A. Dawson
Author: W.R. Forman
Author: F. de Gasperin
Author: C. Jones
Author: G.K. Miley
Author: L. Rudnick
Author: C.L. Sarazin
Author: A. Bonafede
Author: P.N. Best
Author: L. Bîrzan
Author: R. Cassano
Author: K.T. Chyży
Author: J.H. Croston
Author: T. Ensslin
Author: C. Ferrari
Author: M. Hoeft
Author: C. Horellou
Author: M.J. Jarvis
Author: R.P. Kraft
Author: M. Mevius
Author: H.T. Intema
Author: S.S. Murray
Author: E. Orrú
Author: R. Pizzo
Author: A. Simionescu
Author: A. Stroe
Author: S. van der Tol
Author: G.J. White

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