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Title: LOFAR facet callibration

Abstract

LOFAR, the Low-Frequency Array, is a powerful new radio telescope operating between 10 and 240 MHz. LOFAR allows detailed sensitive high-resolution studies of the low-frequency radio sky. At the same time LOFAR also provides excellent short baseline coverage to map di use extended emission. However, producing high-quality deep images is challenging due to the presence of direction dependent calibration errors, caused by imperfect knowledge of the station beam shapes and the ionosphere. Furthermore, the large data volume and presence of station clock errors present additional di culties. In this paper we present a new calibration scheme, which we name facet calibration, to obtain deep high-resolution LOFAR High Band Antenna images using the Dutch part of the array. This scheme solves and corrects the direction dependent errors in a number of facets that cover the observed eld of view. Facet calibration provides close to thermal noise limited images for a typical 8 hr observing run at ~5'' resolution, meeting the speci cations of the LOFAR Tier-1 northern survey.

Authors:
 [1];  [2];  [3];  [4];  [5];  [6];  [7];  [7];  [8];  [9];  [5];  [1];  [1];  [4];  [10];  [1];  [11];  [1];  [4];  [12] more »;  [13];  [5];  [6];  [5];  [9];  [14];  [15];  [16];  [17];  [18];  [19];  [20];  [1];  [8];  [21];  [22];  [8];  [8];  [23];  [4];  [8];  [24] « less
  1. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  2. Leiden Univ. (Netherlands); Netherlands Inst. for Radio Astronomy, Dwingeloo (Netherlands); Univ. of Hertfordshire, Hatfield (United Kingdom)
  3. Univ. of Hertfordshire, Hatfield (United Kingdom)
  4. Leiden Univ. (Netherlands)
  5. Hamburger Sternwarte (Germany)
  6. Univ. of Edinburgh, Scotland (United Kingdom)
  7. Netherlands Inst. for Radio Astronomy, Dwingeloo (Netherlands); Kapteyn Astronomical Inst., Groningen (Netherlands)
  8. Netherlands Inst. for Radio Astronomy, Dwingeloo (Netherlands)
  9. Istituto Nazionale di Astrofisica (INAF), Bologna (Italy)
  10. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  11. Leiden Univ. (Netherlands); Hamburger Sternwarte (Germany)
  12. Univ. of Minnesota, Minneapolis, MN (United States)
  13. Univ. of Virginia, Charlottesville, VA (United States)
  14. Jagiellonian Univ., Krakow (Poland)
  15. Univ. of Southampton (United Kingdom)
  16. Max Planck Society, Garching (Germany). Max Planck Inst. for Astrophysics
  17. Univ. Cote d'Azur, Nice (France)
  18. Thuringer Landessternwarte Tautenburg (Germany)
  19. Chalmers Univ. of Technology, Onsala (Sweden)
  20. Oxford Astrophysics (United Kingdom); Univ. of West Cape, Bellville (South Africa)
  21. Leiden Univ. (Netherlands); National Radio Astronomy Observatory, Socorro, NM (United States)
  22. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Johns Hopkins Univ., Baltimore, MD (United States)
  23. Inst. of Space and Astronautical Science, Kanagawa (Japan)
  24. The Open Univ., Milton Keynes (United Kingdom); Science and Technology Facilities Council (STFC), Oxford (United Kingdom). Rutherford Appleton Lab. (RAL)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1430950
Report Number(s):
LLNL-JRNL-740740
Journal ID: ISSN 1538-4365; TRN: US1803005
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal. Supplement Series (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal. Supplement Series (Online); Journal Volume: 223; Journal Issue: 1; Journal ID: ISSN 1538-4365
Publisher:
American Astronomical Society/IOP
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS

Citation Formats

Weeren, R. J. van, Williams, W. L., Hardcastle, M. J., Shimwell, T. W., Rafferty, D. A., Sabater, J., Heald, G., Sridhar, S. S., Dijkema, T. J., Brunetti, G., Bruggen, M., Andrade-Santos, F., Ogrean, G. A., Rottgering, H. J. A., Dawson, W. A., Forman, W. R., Gasperin, F. de, Jones, C., Miley, G. K., Rudnick, L., Sarazin, C. L., Bonafede, A., Best, P. N., Birzan, L., Cassano, R., Chyzy, K. T., Croston, J. H., Ensslin, T., Ferrari, C., Hoeft, M., Horellou, C., Jarvis, M. J., Kraft, R. P., Mevius, M., Intema, H. T., Murray, S. S., Orru, E., Pizzo, R., Simionescu, A., Stroe, A., van der Tol, S., and White, G. J. LOFAR facet callibration. United States: N. p., 2016. Web. doi:10.3847/0067-0049/223/1/2.
Weeren, R. J. van, Williams, W. L., Hardcastle, M. J., Shimwell, T. W., Rafferty, D. A., Sabater, J., Heald, G., Sridhar, S. S., Dijkema, T. J., Brunetti, G., Bruggen, M., Andrade-Santos, F., Ogrean, G. A., Rottgering, H. J. A., Dawson, W. A., Forman, W. R., Gasperin, F. de, Jones, C., Miley, G. K., Rudnick, L., Sarazin, C. L., Bonafede, A., Best, P. N., Birzan, L., Cassano, R., Chyzy, K. T., Croston, J. H., Ensslin, T., Ferrari, C., Hoeft, M., Horellou, C., Jarvis, M. J., Kraft, R. P., Mevius, M., Intema, H. T., Murray, S. S., Orru, E., Pizzo, R., Simionescu, A., Stroe, A., van der Tol, S., & White, G. J. LOFAR facet callibration. United States. doi:10.3847/0067-0049/223/1/2.
Weeren, R. J. van, Williams, W. L., Hardcastle, M. J., Shimwell, T. W., Rafferty, D. A., Sabater, J., Heald, G., Sridhar, S. S., Dijkema, T. J., Brunetti, G., Bruggen, M., Andrade-Santos, F., Ogrean, G. A., Rottgering, H. J. A., Dawson, W. A., Forman, W. R., Gasperin, F. de, Jones, C., Miley, G. K., Rudnick, L., Sarazin, C. L., Bonafede, A., Best, P. N., Birzan, L., Cassano, R., Chyzy, K. T., Croston, J. H., Ensslin, T., Ferrari, C., Hoeft, M., Horellou, C., Jarvis, M. J., Kraft, R. P., Mevius, M., Intema, H. T., Murray, S. S., Orru, E., Pizzo, R., Simionescu, A., Stroe, A., van der Tol, S., and White, G. J. Mon . "LOFAR facet callibration". United States. doi:10.3847/0067-0049/223/1/2. https://www.osti.gov/servlets/purl/1430950.
@article{osti_1430950,
title = {LOFAR facet callibration},
author = {Weeren, R. J. van and Williams, W. L. and Hardcastle, M. J. and Shimwell, T. W. and Rafferty, D. A. and Sabater, J. and Heald, G. and Sridhar, S. S. and Dijkema, T. J. and Brunetti, G. and Bruggen, M. and Andrade-Santos, F. and Ogrean, G. A. and Rottgering, H. J. A. and Dawson, W. A. and Forman, W. R. and Gasperin, F. de and Jones, C. and Miley, G. K. and Rudnick, L. and Sarazin, C. L. and Bonafede, A. and Best, P. N. and Birzan, L. and Cassano, R. and Chyzy, K. T. and Croston, J. H. and Ensslin, T. and Ferrari, C. and Hoeft, M. and Horellou, C. and Jarvis, M. J. and Kraft, R. P. and Mevius, M. and Intema, H. T. and Murray, S. S. and Orru, E. and Pizzo, R. and Simionescu, A. and Stroe, A. and van der Tol, S. and White, G. J.},
abstractNote = {LOFAR, the Low-Frequency Array, is a powerful new radio telescope operating between 10 and 240 MHz. LOFAR allows detailed sensitive high-resolution studies of the low-frequency radio sky. At the same time LOFAR also provides excellent short baseline coverage to map di use extended emission. However, producing high-quality deep images is challenging due to the presence of direction dependent calibration errors, caused by imperfect knowledge of the station beam shapes and the ionosphere. Furthermore, the large data volume and presence of station clock errors present additional di culties. In this paper we present a new calibration scheme, which we name facet calibration, to obtain deep high-resolution LOFAR High Band Antenna images using the Dutch part of the array. This scheme solves and corrects the direction dependent errors in a number of facets that cover the observed eld of view. Facet calibration provides close to thermal noise limited images for a typical 8 hr observing run at ~5'' resolution, meeting the speci cations of the LOFAR Tier-1 northern survey.},
doi = {10.3847/0067-0049/223/1/2},
journal = {The Astrophysical Journal. Supplement Series (Online)},
number = 1,
volume = 223,
place = {United States},
year = {2016},
month = {3}
}

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