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Journal Articles Astronomy and Astrophysics - A&A Year : 2015

The LOFAR long baseline snapshot calibrator survey

J. Moldón (1) , A. T. Deller , O. Wucknitz (2) , N. Jackson (3) , A. Drabent (4) , T. Carozzi (5) , J. Conway (6) , A. D. Kapińska (7) , P. Mckean (1) , L. Morabito (8) , E. Varenius (6) , P. Zarka (9, 10) , J. Anderson (11) , A. Asgekar (1) , I. M. Avruch (12) , M. E. Bell (13) , M. J. Bentum (1) , G. Bernardi , P. Best (14) , L. Bîrzan (15) , J. Bregman (1) , F. Breitling (16) , J. W. Broderick (17) , M. Brüggen (18) , H. R. Butcher (19) , D. Carbone (20) , B. Ciardi (21) , F. de Gasperin (22) , E. de Geus (23) , S. Duscha (1) , J. Eislöffel (4) , D. Engels (22) , H. Falcke (24) , R. A. Fallows (25) , R. Fender (17) , C. Ferrari (26) , W. Frieswijk , M. A. Garrett (15) , Jean-Mathias Griessmeier (27, 28) , A. W. Gunst (1) , J. P. Hamaker (1) , T. E. Hassall (3) , G. Heald , M. Hoeft (4) , E. Juette (29) , A. Karastergiou (30) , V. I. Kondratiev , M. Kramer (31, 32) , M. Kuniyoshi (31) , G. Kuper , P. Maat , G. Mann (16) , S. Markoff (33) , R. Mcfadden (1) , D. Mckay-Bukowski (34) , R. Morganti (35, 1) , H. Munk (1) , M. J. Norden , A. R. Offringa (35, 36) , E. Orru , H. Paas (37) , M. Pandey-Pommier (38) , R. Pizzo , A. G. Polatidis , W. Reich (31) , H. Röttgering (15) , A. Rowlinson , A. M. M. Scaife (39) , D. Schwarz (40) , J. Sluman , O. Smirnov (41) , B. W. Stappers (3) , M. Steinmetz (42) , Michel Tagger (28) , Y. Tang (43) , C. Tasse (10, 44) , S. Thoudam (24) , M. C. Toribio (45) , R. Vermeulen , C. Vocks (16) , R. J. van Weeren , S. White , M. W. Wise (33) , S. Yatawatta , A. Zensus (31)
1 ASTRON - Netherlands Institute for Radio Astronomy
2 AlfA - Argelander-Institut für Astronomie
3 Jodrell Bank Centre for Astrophysics
4 TLS - Thüringer Landessternwarte Tautenburg
5 OSO - Onsala Space Observatory
6 Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology
7 CAS - ARC Centre of Excellence for Autonomous Systems
8 Leiden Observatory - Leiden Observatory, Leiden University
9 OP - Observatoire de Paris - Site de Paris
10 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
11 Institute for Mathematics Applied to Geoscience
12 SRON - SRON Netherlands Institute for Space Research
13 CSIRO Astronomy and Space Science
14 University of Edinburgh
15 Leiden Observatory [Leiden]
16 AIP - Leibniz-Institut für Astrophysik Potsdam
17 University of Southampton
18 Jacobs University = Constructor University [Bremen]
19 RSAA - Research School of Astronomy and Astrophysics [Canberra]
20 UvA - University of Amsterdam [Amsterdam] = Universiteit van Amsterdam
21 Max Planck Institute for Astrophysics
22 Hamburger Sternwarte/Hamburg Observatory
23 Medstar Research Institute
24 Radboud University [Nijmegen]
25 Institute of Mathematical and Physical Sciences
26 Département de Géologie
27 USN - Unité Scientifique de la Station de Nançay
28 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
29 RUB - Ruhr University Bochum = Ruhr-Universität Bochum
30 Oxford Astrophysics
31 MPIFR - Max-Planck-Institut für Radioastronomie
32 CAL - Columbia Astrophysics Laboratory
33 AI PANNEKOEK - Astronomical Institute Anton Pannekoek
34 University of Oulu
35 Kapteyn Astronomical Institute [Groningen]
36 UMR PVBMT - Peuplements végétaux et bioagresseurs en milieu tropical
37 Center for Information Technology CIT
38 CRAL - Centre de Recherche Astrophysique de Lyon
39 School of Physics and Astronomy [Southampton]
40 Interactions Son Musique Mouvement
41 Rhodes University, Grahamstown
42 DSMZ - Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures
43 UP11 - Université Paris-Sud - Paris 11
44 SKA South Africa
45 Finca El Encin
A. T. Deller
  • Function : Author
L. Morabito
  • Function : Author
  • PersonId : 1208612
G. Bernardi
  • Function : Author
P. Best
  • Function : Author
J. Eislöffel
C. Ferrari
W. Frieswijk
  • Function : Author
G. Heald
  • Function : Author
V. I. Kondratiev
  • Function : Author
G. Kuper
  • Function : Author
P. Maat
  • Function : Author
G. Mann
M. J. Norden
  • Function : Author
E. Orru
  • Function : Author
R. Pizzo
A. G. Polatidis
  • Function : Author
H. Röttgering
A. Rowlinson
  • Function : Author
J. Sluman
  • Function : Author
M. C. Toribio
  • Function : Author
R. Vermeulen
  • Function : Author
R. J. van Weeren
  • Function : Author
S. White
  • Function : Author
S. Yatawatta
  • Function : Author

Abstract

Aims. An efficient means of locating calibrator sources for International 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 pre-selected 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. Over 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 density of calibrators on the sky 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.
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Dates and versions

insu-01323110 , version 1 (20-11-2019)

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J. Moldón, A. T. Deller, O. Wucknitz, N. Jackson, A. Drabent, et al.. The LOFAR long baseline snapshot calibrator survey. Astronomy and Astrophysics - A&A, 2015, 574, pp.A73. ⟨10.1051/0004-6361/201425042⟩. ⟨insu-01323110⟩
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