LOFAR Facet Calibration
Journal article, 2016

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 highquality 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 similar to 5. resolution, meeting the specifications of the LOFAR Tier-1 northern survey.

gain calibration

system

sky survey

self-calibration

techniques: interferometric

algorithm

wide-field

astronomy

w-projection

radio interferometric calibration

Author

R. J. van Weeren

Harvard-Smithsonian Center for Astrophysics

W. L. Williams

University of Hertfordshire

Netherlands Institute for Radio Astronomy (ASTRON)

Leiden University

M. J. Hardcastle

University of Hertfordshire

T. W. Shimwell

Leiden University

D. Rafferty

Universität Hamburg

J. Sabater

University of Edinburgh

G. Heald

University of Groningen

Netherlands Institute for Radio Astronomy (ASTRON)

S. S. Sridhar

University of Groningen

Netherlands Institute for Radio Astronomy (ASTRON)

T. J. Dijkema

Netherlands Institute for Radio Astronomy (ASTRON)

G. Brunetti

Istituto di Radioastronomia

M. Brüggen

Universität Hamburg

F. Andrade-Santos

Harvard-Smithsonian Center for Astrophysics

G. Ogrean

Harvard-Smithsonian Center for Astrophysics

H. Rottgering

Leiden University

W. A. Dawson

Lawrence Livermore National Laboratory

W. R. Forman

Harvard-Smithsonian Center for Astrophysics

F. De Gasperin

Universität Hamburg

Leiden University

C. G. Jones

Harvard-Smithsonian Center for Astrophysics

G. Miley

Leiden University

L. Rudnick

University of Minnesota

C. L. Sarazin

University of Virginia

A. Bonafede

Universität Hamburg

P. N. Best

University of Edinburgh

L. Birzan

Universität Hamburg

R. Cassano

Istituto di Radioastronomia

K.T. Chyz̊y

Jagiellonian University in Kraków

J. H. Croston

University of Southampton

T.A. Enßlin

Max Planck Society

C. Ferrari

Observatoire de la Cote d'Azur

M. Hoeft

Thüringer Landessternwarte Tautenburg

Cathy Horellou

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

M. J. Jarvis

University of Oxford

University of the Western Cape

R. P. Kraft

Harvard-Smithsonian Center for Astrophysics

M. Mevius

Netherlands Institute for Radio Astronomy (ASTRON)

H. T. Intema

National Radio Astronomy Observatory

Leiden University

S. S. Murray

Harvard-Smithsonian Center for Astrophysics

Johns Hopkins University

E. Orru

Netherlands Institute for Radio Astronomy (ASTRON)

R. Pizzo

Netherlands Institute for Radio Astronomy (ASTRON)

A. Simionescu

JAXA Institute of Space and Astronautical Science

A. Stroe

Leiden University

S. van der Tol

Netherlands Institute for Radio Astronomy (ASTRON)

G. J. White

Open University

Rutherford Appleton Laboratory

Astrophysical Journal, Supplement Series

0067-0049 (ISSN) 1538-4365 (eISSN)

Vol. 223 1 2

Subject Categories

Astronomy, Astrophysics and Cosmology

DOI

10.3847/0067-0049/223/1/2

More information

Latest update

4/15/2019