LOFAR facet calibration
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 diffuse 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 difficulties. 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 field of view. Facet calibration provides close to thermal noise limited images for a typical 8 hr observing run at 5arcsec resolution, meeting the specifications of the LOFAR Tier-1 northern survey.
Keywords
Cite
@article{arxiv.1601.05422,
title = {LOFAR facet calibration},
author = {R. J. van Weeren and W. L. Williams and M. J. Hardcastle and T. W. Shimwell and D. A. Rafferty and J. Sabater and G. Heald and S. S. Sridhar and T. J. Dijkema and G. Brunetti and M. Brüggen and F. Andrade-Santos and G. A. Ogrean and H. J. A. Röttgering and W. A. Dawson and W. R. Forman and F. de Gasperin and C. Jones and G. K. Miley and L. Rudnick and C. L. Sarazin and A. Bonafede and P. N. Best and L. Bîrzan and R. Cassano and K. T. Chyży and J. H. Croston and T. Ensslin and C. Ferrari and M. Hoeft and C. Horellou and M. J. Jarvis and R. P. Kraft and M. Mevius and H. T. Intema and S. S. Murray and E. Orrú and R. Pizzo and A. Simionescu and A. Stroe and S. van der Tol and G. J. White},
journal= {arXiv preprint arXiv:1601.05422},
year = {2016}
}
Comments
17 pages, 12 figures, accepted for publication in ApJS