LBCS: The LOFAR Long-Baseline Calibrator Survey
Journal article, 2016

We outline the LOFAR Long-Baseline Calibrator Survey (LBCS), whose aim is to identify sources suitable for calibrating the highest-resolution observations made with the International LOFAR Telescope, which include baselines > 1000 km. Suitable sources must contain significant correlated flux density (greater than or similar to 50 - 100 mJy) at frequencies around 110-190 MHz on scales of a few hundred milliarcseconds. At least for the 200-300-km international baselines, we find around 1 suitable calibrator source per square degree over a large part of the northern sky, in agreement with previous work. This should allow a randomly selected target to be successfully phase calibrated on the international baselines in over 50% of cases. Products of the survey include calibrator source lists and fringe-rate and delay maps of wide areas-typically a few degrees-around each source. The density of sources with significant correlated flux declines noticeably with baseline length over the range 200-600 km, with good calibrators on the longest baselines appearing only at the rate of 0.5 per sq. deg. Coherence times decrease from 1-3 min on 200-km baselines to about 1 min on 600-km baselines, suggesting that ionospheric phase variations contain components with scales of a few hundred kilometres. The longest median coherence time, at just over 3 min, is seen on the DE609 baseline, which at 227 km is close to being the shortest. We see median coherence times of between 80 and 110 s on the four longest baselines (580-600 km), and about 2 min for the other baselines. The success of phase transfer from calibrator to target is shown to be influenced by distance, in a manner that suggests a coherence patch at 150-MHz of the order of 1 deg. Although source structures cannot be measured in these observations, we deduce that phase transfer is affected if the calibrator source structure is not known. We give suggestions for calibration strategies and choice of calibrator sources, and describe the access to the online catalogue and data products.

radio continuum: galaxies

galaxies: active

instrumentation: interferometers

surveys

techniques: interferometric

Author

N. Jackson

University of Manchester

A. Tagore

University of Manchester

A. Deller

Netherlands Institute for Radio Astronomy (ASTRON)

J. Moldon

University of Manchester

Netherlands Institute for Radio Astronomy (ASTRON)

Eskil Varenius

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

L. Morabito

Leiden University

O. Wucknitz

Max Planck Society

Tobia Carozzi

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

John Conway

Chalmers, Earth and Space Sciences, Onsala Space Observatory

A. Drabent

Tháringer Landessternwarte Tautenburg

A. D. Kapinska

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

University of Portsmouth

University of Western Australia

E. Orru

Netherlands Institute for Radio Astronomy (ASTRON)

M. Brentjens

Netherlands Institute for Radio Astronomy (ASTRON)

R. Blaauw

Netherlands Institute for Radio Astronomy (ASTRON)

G. Kuper

Netherlands Institute for Radio Astronomy (ASTRON)

J. Sluman

Netherlands Institute for Radio Astronomy (ASTRON)

J. Schaap

Netherlands Institute for Radio Astronomy (ASTRON)

N. Vermaas

Netherlands Institute for Radio Astronomy (ASTRON)

M. Iacobelli

Netherlands Institute for Radio Astronomy (ASTRON)

L. Cerrigone

Netherlands Institute for Radio Astronomy (ASTRON)

A. Shulevski

Netherlands Institute for Radio Astronomy (ASTRON)

S. ter Veen

Netherlands Institute for Radio Astronomy (ASTRON)

R. A. Fallows

Netherlands Institute for Radio Astronomy (ASTRON)

R. Pizzo

Netherlands Institute for Radio Astronomy (ASTRON)

M. Sipior

Netherlands Institute for Radio Astronomy (ASTRON)

J. Anderson

German Research Centre for Geosciences (GFZ)

I. M. Avruch

University of Groningen

Netherlands Institute for Space Research (SRON)

M. E. Bell

CSIRO Astronomy and Space Science

I. van Bemmel

Joint Institute for VLBI in Europe (JIVE)

M. J. Bentum

Netherlands Institute for Radio Astronomy (ASTRON)

University of Twente

P. Best

University of Edinburgh

A. Bonafede

University of Hamburg

F. Breitling

Leibniz Institute for Astrophysics Potsdam

J. W. Broderick

Netherlands Institute for Radio Astronomy (ASTRON)

W. N. Brouw

Netherlands Institute for Radio Astronomy (ASTRON)

University of Groningen

M. Brüggen

University of Hamburg

B. Ciardi

Max Planck Society

A. Corstanje

Radboud University

F. De Gasperin

Leiden University

E. de Geus

Netherlands Institute for Radio Astronomy (ASTRON)

SmarterVision BV

J. Eisloffel

Max Planck Society

D. Engels

University of Hamburg

H. Falcke

Netherlands Institute for Radio Astronomy (ASTRON)

Radboud University

M. A. Garrett

Netherlands Institute for Radio Astronomy (ASTRON)

Leiden University

J. M. Griessmeier

University of Orléans

A. W. Gunst

Netherlands Institute for Radio Astronomy (ASTRON)

M. P. van Haarlem

Netherlands Institute for Radio Astronomy (ASTRON)

G. Heald

University of Groningen

CSIRO Astronomy and Space Science

Netherlands Institute for Radio Astronomy (ASTRON)

M. Hoeft

Tháringer Landessternwarte Tautenburg

J. Horandel

Radboud University

A. Horneffer

Max Planck Society

H. Intema

National Radio Astronomy Observatory Socorro

Leiden University

E. Juette

Ruhr-Universität Bochum

M. Kuniyoshi

National Astronomical Observatory of Japan

J. van Leeuwen

Netherlands Institute for Radio Astronomy (ASTRON)

University of Amsterdam

G. M. Loose

Netherlands Institute for Radio Astronomy (ASTRON)

P. Maat

Netherlands Institute for Radio Astronomy (ASTRON)

R. McFadden

Netherlands Institute for Radio Astronomy (ASTRON)

D. McKay-Bukowski

Sodankyla Geophysical Observatory

STFC Rutherford Appleton Laboratory

J. P. McKean

University of Groningen

Netherlands Institute for Radio Astronomy (ASTRON)

D. D. Mulcahy

University of Manchester

H. Munk

Netherlands Institute for Radio Astronomy (ASTRON)

Radboud University

M. Pandey-Pommier

Lyon Observatory

A. G. Polatidis

Netherlands Institute for Radio Astronomy (ASTRON)

W. Reich

Max Planck Society

H. Rottgering

Leiden University

A. Rowlinson

University of Amsterdam

Netherlands Institute for Radio Astronomy (ASTRON)

A. M. M. Scaife

University of Manchester

D. J. Schwarz

Bielefeld University

M. Steinmetz

Leibniz Institute for Astrophysics Potsdam

J. Swinbank

Princeton University

S. Thoudam

Radboud University

M. C. Toribio

Netherlands Institute for Radio Astronomy (ASTRON)

Leiden University

R. Vermeulen

Netherlands Institute for Radio Astronomy (ASTRON)

C. Vocks

Leibniz Institute for Astrophysics Potsdam

R. J. van Weeren

Harvard-Smithsonian Center for Astrophysics

M. W. Wise

University of Amsterdam

Netherlands Institute for Radio Astronomy (ASTRON)

S. Yatawatta

Netherlands Institute for Radio Astronomy (ASTRON)

P. Zarka

LESIA - Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique

Astronomy and Astrophysics

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

Vol. 595 Art no A86- A86

Advanced Radio Astronomy in Europe (RADIONET3)

European Commission (EC) (EC/FP7/283393), 2012-01-01 -- 2015-12-31.

Subject Categories

Astronomy, Astrophysics and Cosmology

DOI

10.1051/0004-6361/201629016

More information

Latest update

7/8/2021 6