LBCS: The LOFAR long baseline snapshot calibrator survey
Artikel i vetenskaplig tidskrift, 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.
instrumentation: interferometers
catalogs
techniques: high angular resolution
methods: observational
instrumentation: high angular resolution
techniques: interferometric
Författare
J. Moldon
Netherlands Institute for Radio Astronomy (ASTRON)
A. T. Deller
Netherlands Institute for Radio Astronomy (ASTRON)
O. Wucknitz
Max-Planck Institut für Radioastronomie
N. Jackson
University of Manchester
A. Drabent
Thüringer Landessternwarte Tautenburg
Tobia Carozzi
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
John Conway
Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium
A. D. Kapinska
ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
Curtin University
University of Portsmouth
J. P. McKean
Netherlands Institute for Radio Astronomy (ASTRON)
L. Morabito
Universiteit Leiden
Eskil Varenius
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
P. Zarka
Centre national de la recherche scientifique (CNRS)
J. Anderson
Deutsches GeoForschungsZentrum (GFZ)
A. Asgekar
Netherlands Institute for Radio Astronomy (ASTRON)
Shell Technology Center
I. M. Avruch
Netherlands Institute for Space Research (SRON)
Kapteyn Astronomical Institute
M. E. Bell
CSIRO Astronomy and Space Science
M. J. Bentum
Universiteit Twente
Netherlands Institute for Radio Astronomy (ASTRON)
G. Bernardi
Harvard-Smithsonian Center for Astrophysics
P. Best
University of Edinburgh
L. Birzan
Universiteit Leiden
J. Bregman
Netherlands Institute for Radio Astronomy (ASTRON)
F. Breitling
Leibniz-Institut Für Astrophysik Potsdam
J. W. Broderick
University of Oxford
University of Southampton
M. Brüggen
Universität Hamburg
H. R. Butcher
Australian National University
D. Carbone
Universiteit Van Amsterdam
B. Ciardi
MPIA
F. De Gasperin
Universität Hamburg
E. de Geus
SmarterVision BV
Netherlands Institute for Radio Astronomy (ASTRON)
S. Duscha
Netherlands Institute for Radio Astronomy (ASTRON)
J. Eisloffel
Thüringer Landessternwarte Tautenburg
D. Engels
Universität Hamburg
H. Falcke
Netherlands Institute for Radio Astronomy (ASTRON)
Radboud Universiteit
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
Universiteit Leiden
Netherlands Institute for Radio Astronomy (ASTRON)
J. Griessmeier
Universite d'Orleans
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
University of Manchester
Max-Planck Institut für Radioastronomie
M. Kuniyoshi
Max-Planck Institut für Radioastronomie
G. Kuper
Netherlands Institute for Radio Astronomy (ASTRON)
P. Maat
Netherlands Institute for Radio Astronomy (ASTRON)
G. Mann
Leibniz-Institut Für Astrophysik Potsdam
S. Markoff
Universiteit Van Amsterdam
R. McFadden
Netherlands Institute for Radio Astronomy (ASTRON)
D. McKay-Bukowski
Oulun Yliopisto
STFC Rutherford Appleton Laboratory
R. Morganti
Netherlands Institute for Radio Astronomy (ASTRON)
Kapteyn Astronomical Institute
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
Rijksuniversiteit 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 Institut für Radioastronomie
H. Rottgering
Universiteit Leiden
A. Rowlinson
CSIRO Astronomy and Space Science
A. M. M. Scaife
University of Southampton
D. Schwarz
Universität Bielefeld
J. Sluman
Netherlands Institute for Radio Astronomy (ASTRON)
O. Smirnov
Square Kilometre Array, South Africa
Rhodes University
B. W. Stappers
University of Manchester
M. Steinmetz
Leibniz-Institut Für Astrophysik Potsdam
M. Tagger
Universite d'Orleans
Y. Tang
Netherlands Institute for Radio Astronomy (ASTRON)
C. Tasse
Universität Bielefeld
S. Thoudam
Radboud Universiteit
M. C. Toribio
Netherlands Institute for Radio Astronomy (ASTRON)
R. Vermeulen
Netherlands Institute for Radio Astronomy (ASTRON)
C. Vocks
Leibniz-Institut Für Astrophysik Potsdam
R. J. van Weeren
Harvard-Smithsonian Center for Astrophysics
S. White
Max-Planck Institut für Radioastronomie
M. W. Wise
Netherlands Institute for Radio Astronomy (ASTRON)
Universiteit Van Amsterdam
S. Yatawatta
Netherlands Institute for Radio Astronomy (ASTRON)
A. Zensus
Max-Planck Institut für Radioastronomie
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 574 Art. no. A73- 25042Ämneskategorier
Astronomi, astrofysik och kosmologi
DOI
10.1051/0004-6361/201425042