LBCS: The LOFAR Long-Baseline Calibrator Survey
Artikel i vetenskaplig tidskrift, 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.

surveys

galaxies: active

radio continuum: galaxies

techniques: interferometric

instrumentation: interferometers

Författare

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, Rymd- och geovetenskap, Radioastronomi och astrofysik

L. Morabito

Leiden University

O. Wucknitz

Max Planck-institutet

Tobia Carozzi

Onsala Space Observatory

John Conway

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

A. Drabent

Tháringer Landessternwarte Tautenburg

A. D. Kapinska

University of Western Australia

University of Portsmouth

CAASTRO

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

Deutsches GeoForschungsZentrum (GFZ)

I. M. Avruch

University of Groningen, Kapteyn Astronomical Institute

SRON Netherlands Institute for Space Research

M. E. Bell

CSIRO Astronomy and Space Science

I. van Bemmel

Joint Institute for VLBI in Europe

M. J. Bentum

University of Twente

Netherlands Institute for Radio Astronomy (ASTRON)

P. Best

University of Edinburgh

A. Bonafede

Universität Hamburg

F. Breitling

Astrophysikalisches Institut Potsdam

J. W. Broderick

Netherlands Institute for Radio Astronomy (ASTRON)

W. N. Brouw

University of Groningen, Kapteyn Astronomical Institute

Netherlands Institute for Radio Astronomy (ASTRON)

M. Brüggen

Universität Hamburg

B. Ciardi

Max Planck-institutet

A. Corstanje

Radboud Universiteit

F. De Gasperin

Leiden University

E. de Geus

Netherlands Institute for Radio Astronomy (ASTRON)

SmarterVision BV

J. Eisloffel

Max Planck-institutet

D. Engels

Universität Hamburg

H. Falcke

Netherlands Institute for Radio Astronomy (ASTRON)

Radboud Universiteit

M. A. Garrett

Netherlands Institute for Radio Astronomy (ASTRON)

Leiden University

J. M. Griessmeier

Universite d'Orleans

A. W. Gunst

Netherlands Institute for Radio Astronomy (ASTRON)

M. P. van Haarlem

Netherlands Institute for Radio Astronomy (ASTRON)

G. Heald

CSIRO Astronomy and Space Science

University of Groningen, Kapteyn Astronomical Institute

Netherlands Institute for Radio Astronomy (ASTRON)

M. Hoeft

Tháringer Landessternwarte Tautenburg

J. Horandel

Radboud Universiteit

A. Horneffer

Max Planck-institutet

H. Intema

Leiden University

National Radio Astronomy Observatory Socorro

E. Juette

Ruhr-Universität Bochum

M. Kuniyoshi

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

J. van Leeuwen

Universiteit Van Amsterdam

Netherlands Institute for Radio Astronomy (ASTRON)

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

Rutherford Appleton Laboratory

Sodankyla Geophysical Observatory

J. P. McKean

Netherlands Institute for Radio Astronomy (ASTRON)

University of Groningen, Kapteyn Astronomical Institute

D. D. Mulcahy

University of Manchester

H. Munk

Radboud Universiteit

Netherlands Institute for Radio Astronomy (ASTRON)

M. Pandey-Pommier

Observatoire de Lyon

A. G. Polatidis

Netherlands Institute for Radio Astronomy (ASTRON)

W. Reich

Max Planck-institutet

H. Rottgering

Leiden University

A. Rowlinson

Universiteit Van Amsterdam

Netherlands Institute for Radio Astronomy (ASTRON)

A. M. M. Scaife

University of Manchester

D. J. Schwarz

Universität Bielefeld

M. Steinmetz

Astrophysikalisches Institut Potsdam

J. Swinbank

Princeton University

S. Thoudam

Radboud Universiteit

M. C. Toribio

Netherlands Institute for Radio Astronomy (ASTRON)

Leiden University

R. Vermeulen

Netherlands Institute for Radio Astronomy (ASTRON)

C. Vocks

Astrophysikalisches Institut Potsdam

R. J. van Weeren

Harvard-Smithsonian Center for Astrophysics

M. W. Wise

Universiteit Van 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

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.1051/0004-6361/201629016