LBCS: The LOFAR long baseline snapshot calibrator survey
Journal article, 2015

Aims. An efficient means of locating calibrator sources for international LOw Frequency ARray (LOFAR) is developed and used to determine the average density of usable calibrator sources on the sky for subarcsecond observations at 140 MHz. Methods. We used the multi-beaming capability of LOFAR to conduct a fast and computationally inexpensive survey with the full international LOFAR array. Sources were preselected on the basis of 325 MHz arcminute-scale flux density using existing catalogues. By observing 30 different sources in each of the 12 sets of pointings per hour, we were able to inspect 630 sources in two hours to determine if they possess a sufficiently bright compact component to be usable as LOFAR delay calibrators. Results. More than 40% of the observed sources are detected on multiple baselines between international stations and 86 are classified as satisfactory calibrators. We show that a flat low-frequency spectrum (from 74 to 325 MHz) is the best predictor of compactness at 140 MHz. We extrapolate from our sample to show that the sky density of calibrators that are sufficiently bright to calibrate dispersive and non-dispersive delays for the international LOFAR using existing methods is 1.0 per square degree. Conclusions. The observed density of satisfactory delay calibrator sources means that observations with international LOFAR should be possible at virtually any point in the sky provided that a fast and efficient search, using the methodology described here, is conducted prior to the observation to identify the best calibrator.

methods: observational

techniques: high angular resolution

catalogs

instrumentation: high angular resolution

techniques: interferometric

instrumentation: interferometers

Author

J. Moldon

Netherlands Institute for Radio Astronomy (ASTRON)

A. T. Deller

Netherlands Institute for Radio Astronomy (ASTRON)

O. Wucknitz

Max-Planck Institute for Radio Astronomy

N. Jackson

University of Manchester

A. Drabent

Thüringer Landessternwarte Tautenburg

Tobia Carozzi

Chalmers, Earth and Space Sciences, Onsala Space Observatory

John Conway

Chalmers, Earth and Space Sciences, Onsala Space Observatory

A. D. Kapinska

Curtin University

ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)

University of Portsmouth

J. P. McKean

Netherlands Institute for Radio Astronomy (ASTRON)

L. Morabito

Leiden University

Eskil Varenius

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

P. Zarka

Centre national de la recherche scientifique (CNRS)

J. Anderson

German Research Centre for Geosciences (GFZ)

A. Asgekar

Netherlands Institute for Radio Astronomy (ASTRON)

Shell Technology Center

I. M. Avruch

Kapteyn Astronomical Institute

Netherlands Institute for Space Research (SRON)

M. E. Bell

CSIRO Astronomy and Space Science

M. J. Bentum

Netherlands Institute for Radio Astronomy (ASTRON)

University of Twente

G. Bernardi

Harvard-Smithsonian Center for Astrophysics

P. Best

University of Edinburgh

L. Birzan

Leiden University

J. Bregman

Netherlands Institute for Radio Astronomy (ASTRON)

F. Breitling

Leibniz Institute for Astrophysics Potsdam

J. W. Broderick

University of Oxford

University of Southampton

M. Brüggen

Universität Hamburg

H. R. Butcher

Australian National University

D. Carbone

University of Amsterdam

B. Ciardi

MPIA

F. De Gasperin

Universität Hamburg

E. de Geus

Netherlands Institute for Radio Astronomy (ASTRON)

SmarterVision BV

S. Duscha

Netherlands Institute for Radio Astronomy (ASTRON)

J. Eisloffel

Thüringer Landessternwarte Tautenburg

D. Engels

Universität Hamburg

H. Falcke

Radboud University

Netherlands Institute for Radio Astronomy (ASTRON)

R. A. Fallows

Netherlands Institute for Radio Astronomy (ASTRON)

R. Fender

University of Oxford

C. Ferrari

Centre national de la recherche scientifique (CNRS)

W. Frieswijk

Netherlands Institute for Radio Astronomy (ASTRON)

M. A. Garrett

Netherlands Institute for Radio Astronomy (ASTRON)

Leiden University

J. Griessmeier

University of Orléans

A. W. Gunst

Netherlands Institute for Radio Astronomy (ASTRON)

J. P. Hamaker

Netherlands Institute for Radio Astronomy (ASTRON)

T. E. Hassall

University of Southampton

G. Heald

Netherlands Institute for Radio Astronomy (ASTRON)

M. Hoeft

Thüringer Landessternwarte Tautenburg

B. Juette

Ruhr-Universität Bochum

A. Karastergiou

University of Oxford

V. I. Kondratiev

Astro Space Center of Lebedev Physical Institute

Netherlands Institute for Radio Astronomy (ASTRON)

M. Kramer

Max-Planck Institute for Radio Astronomy

University of Manchester

M. Kuniyoshi

Max-Planck Institute for Radio Astronomy

G. Kuper

Netherlands Institute for Radio Astronomy (ASTRON)

P. Maat

Netherlands Institute for Radio Astronomy (ASTRON)

G. Mann

Astrophysikalisches Institut Potsdam

S. Markoff

University of Amsterdam

R. McFadden

Netherlands Institute for Radio Astronomy (ASTRON)

D. McKay-Bukowski

University of Oulu

STFC Rutherford Appleton Laboratory

R. Morganti

Kapteyn Astronomical Institute

Netherlands Institute for Radio Astronomy (ASTRON)

H. Munk

Netherlands Institute for Radio Astronomy (ASTRON)

M. J. Norden

Netherlands Institute for Radio Astronomy (ASTRON)

A. R. Offringa

Australian National University

E. Orru

Netherlands Institute for Radio Astronomy (ASTRON)

H. Paas

University of Groningen

M. Pandey-Pommier

Observatoire de Lyon

R. Pizzo

Netherlands Institute for Radio Astronomy (ASTRON)

A. G. Polatidis

Netherlands Institute for Radio Astronomy (ASTRON)

W. Reich

Max-Planck Institute for Radio Astronomy

H. Rottgering

Leiden University

A. Rowlinson

CSIRO Astronomy and Space Science

A. M. M. Scaife

University of Southampton

D. Schwarz

Bielefeld University

J. Sluman

Netherlands Institute for Radio Astronomy (ASTRON)

O. Smirnov

Rhodes University

SKA South Africa

B. W. Stappers

University of Manchester

M. Steinmetz

Leibniz Institute for Astrophysics Potsdam

M. Tagger

University of Orléans

Y. Tang

Netherlands Institute for Radio Astronomy (ASTRON)

C. Tasse

Bielefeld University

S. Thoudam

Radboud University

M. C. Toribio

Netherlands Institute for Radio Astronomy (ASTRON)

R. Vermeulen

Netherlands Institute for Radio Astronomy (ASTRON)

C. Vocks

Leibniz Institute for Astrophysics Potsdam

R. J. van Weeren

Harvard-Smithsonian Center for Astrophysics

S. White

Max-Planck Institute for Radio Astronomy

M. W. Wise

University of Amsterdam

Netherlands Institute for Radio Astronomy (ASTRON)

S. Yatawatta

Netherlands Institute for Radio Astronomy (ASTRON)

A. Zensus

Max-Planck Institute for Radio Astronomy

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 574 Art. no. A73- 25042

Subject Categories

Astronomy, Astrophysics and Cosmology

DOI

10.1051/0004-6361/201425042

More information

Latest update

3/3/2020 3