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.
galaxies: active
surveys
instrumentation: interferometers
radio continuum: galaxies
techniques: interferometric
Författare
N. Jackson
University of Manchester
A. Tagore
University of Manchester
A. Deller
Netherlands Institute for Radio Astronomy (ASTRON)
J. Moldon
Netherlands Institute for Radio Astronomy (ASTRON)
University of Manchester
Eskil Varenius
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
L. Morabito
Universiteit Leiden
O. Wucknitz
Max-Planck-Gesellschaft
Tobia Carozzi
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
John Conway
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
A. Drabent
Thüringer 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
Deutsches GeoForschungsZentrum (GFZ)
I. M. Avruch
Rijksuniversiteit Groningen
Netherlands Institute for Space Research (SRON)
M. E. Bell
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
I. van Bemmel
Joint Institute for VLBI in Europe (JIVE)
M. J. Bentum
Universiteit Twente
Netherlands Institute for Radio Astronomy (ASTRON)
P. Best
University of Edinburgh
A. Bonafede
Universität Hamburg
F. Breitling
Leibniz-Institut Für Astrophysik Potsdam
J. W. Broderick
Netherlands Institute for Radio Astronomy (ASTRON)
W. N. Brouw
Rijksuniversiteit Groningen
Netherlands Institute for Radio Astronomy (ASTRON)
M. Brüggen
Universität Hamburg
B. Ciardi
Max-Planck-Gesellschaft
A. Corstanje
Radboud Universiteit
F. De Gasperin
Universiteit Leiden
E. de Geus
Netherlands Institute for Radio Astronomy (ASTRON)
SmarterVision BV
J. Eisloffel
Max-Planck-Gesellschaft
D. Engels
Universität Hamburg
H. Falcke
Radboud Universiteit
Netherlands Institute for Radio Astronomy (ASTRON)
M. A. Garrett
Netherlands Institute for Radio Astronomy (ASTRON)
Universiteit Leiden
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
Netherlands Institute for Radio Astronomy (ASTRON)
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
Rijksuniversiteit Groningen
M. Hoeft
Thüringer Landessternwarte Tautenburg
J. Horandel
Radboud Universiteit
A. Horneffer
Max-Planck-Gesellschaft
H. Intema
Universiteit Leiden
National Radio Astronomy Observatory Socorro
E. Juette
Ruhr-Universität Bochum
M. Kuniyoshi
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
STFC Rutherford Appleton Laboratory
Sodankyla Geophysical Observatory
J. P. McKean
Rijksuniversiteit Groningen
Netherlands Institute for Radio Astronomy (ASTRON)
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-Gesellschaft
H. Rottgering
Universiteit Leiden
A. Rowlinson
Netherlands Institute for Radio Astronomy (ASTRON)
Universiteit Van Amsterdam
A. M. M. Scaife
University of Manchester
D. J. Schwarz
Universität Bielefeld
M. Steinmetz
Leibniz-Institut Für Astrophysik Potsdam
J. Swinbank
Princeton University
S. Thoudam
Radboud Universiteit
M. C. Toribio
Netherlands Institute for Radio Astronomy (ASTRON)
Universiteit Leiden
R. Vermeulen
Netherlands Institute for Radio Astronomy (ASTRON)
C. Vocks
Leibniz-Institut Für Astrophysik Potsdam
R. J. van Weeren
Harvard-Smithsonian Center for Astrophysics
M. W. Wise
Netherlands Institute for Radio Astronomy (ASTRON)
Universiteit Van Amsterdam
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- A86Advanced Radio Astronomy in Europe (RADIONET3)
(EC/FP7/283393), 2012-01-01 -- 2015-12-31.
Ämneskategorier
Astronomi, astrofysik och kosmologi
DOI
10.1051/0004-6361/201629016