University of Hertfordshire Research Archive

        JavaScript is disabled for your browser. Some features of this site may not work without it.

        Browse

        All of UHRABy Issue DateAuthorsTitlesThis CollectionBy Issue DateAuthorsTitles

        Arkivum Files

        My Downloads
        View Item 
        • UHRA Home
        • University of Hertfordshire
        • Research publications
        • View Item
        • UHRA Home
        • University of Hertfordshire
        • Research publications
        • View Item

        Sub-arcsecond imaging with the International LOFAR Telescope. II. Completion of the LOFAR Long-Baseline Calibrator Survey

        View/Open
        Final Accepted Version (PDF, 1Mb)
        Author
        Jackson, Neal
        Badole, Shruti
        Chhetri, Rajan
        Prusis, Kaspars
        Nikolajevs, Atvars
        Morabito, Leah
        Brentjens, Michiel
        Sweijen, Frits
        Iacobelli, Marco
        Orrù, Emanuela
        Sluman, J.
        Blaauw, R.
        Mulder, H.
        Dijk, P. van
        Mooney, Sean
        Deller, Adam
        Moldon, Javier
        Callingham, J. R.
        Harwood, Jeremy
        Hardcastle, Martin
        Heald, George
        Drabent, Alexander
        McKean, J. P.
        Asgekar, A.
        Avruch, I. M.
        Bentum, M. J.
        Bonafede, A.
        Brouw, W. N.
        Brüggen, M.
        Butcher, H. R.
        Ciardi, B.
        Coolen, A.
        Corstanje, A.
        Damstra, S.
        Duscha, S.
        Eislöffel, J.
        Falcke, H.
        Garrett, M.
        Gasperin, F. de
        Griessmeier, J. -M.
        Gunst, A. W.
        Haarlem, M. P. van
        Hoeft, M.
        Horst, A. J. van der
        Jütte, E.
        Koopmans, L. V. E.
        Krankowski, A.
        Maat, P.
        Mann, G.
        Miley, G. K.
        Nelles, A.
        Norden, M.
        Paas, M.
        Pandey, V. N.
        Pandey-Pommier, M.
        Pizzo, R. F.
        Reich, W.
        Rothkaehl, H.
        Rowlinson, A.
        Ruiter, M.
        Shulevski, A.
        Schwarz, D. J.
        Smirnov, O.
        Tagger, M.
        Vocks, C.
        Weeren, R. J. van
        Wijers, R.
        Wucknitz, O.
        Zarka, P.
        Zensus, J. A.
        Zucca, P.
        Attention
        2299/25394
        Abstract
        The Low-Frequency Array (LOFAR) Long-Baseline Calibrator Survey (LBCS) was conducted between 2014 and 2019 in order to obtain a set of suitable calibrators for the LOFAR array. In this paper, we present the complete survey, building on the preliminary analysis published in 2016 which covered approximately half the survey area. The final catalogue consists of 30 006 observations of 24 713 sources in the northern sky, selected for a combination of high low-frequency radio flux density and flat spectral index using existing surveys (WENSS, NVSS, VLSS, and MSSS). Approximately one calibrator per square degree, suitable for calibration of ≥200 km baselines is identified by the detection of compact flux density, for declinations north of 30° and away from the Galactic plane, with a considerably lower density south of this point due to relative difficulty in selecting flat-spectrum candidate sources in this area of the sky. The catalogue contains indicators of degree of correlated flux on baselines between the Dutch core and each of the international stations, involving a maximum baseline length of nearly 2000 km, for all of the observations. Use of the VLBA calibrator list, together with statistical arguments by comparison with flux densities from lower-resolution catalogues, allow us to establish a rough flux density scale for the LBCS observations, so that LBCS statistics can be used to estimate compact flux densities on scales between 300 mas and 2′, for sources observed in the survey. The survey is used to estimate the phase coherence time of the ionosphere for the LOFAR international baselines, with median phase coherence times of about 2 min varying by a few tens of percent between the shortest and longest baselines. The LBCS can be used to assess the structures of point sources in lower-resolution surveys, with significant reductions in the degree of coherence in these sources on scales between 2′ and 300 mas. The LBCS survey sources show a greater incidence of compact flux density in quasars than in radio galaxies, consistent with unified schemes of radio sources. Comparison with samples of sources from interplanetary scintillation (IPS) studies with the MurchisonWidefield Array shows consistent patterns of detection of compact structure in sources observed both interferometrically with LOFAR and using IPS.
        Publication date
        2022-02-01
        Published in
        Astronomy & Astrophysics
        Published version
        https://doi.org/10.1051/0004-6361/202140756
        License
        Unspecified
        Other links
        http://hdl.handle.net/2299/25394
        Relations
        School of Physics, Engineering & Computer Science
        Metadata
        Show full item record
        Keep in touch

        © 2019 University of Hertfordshire

        I want to...

        • Apply for a course
        • Download a Prospectus
        • Find a job at the University
        • Make a complaint
        • Contact the Press Office

        Go to...

        • Accommodation booking
        • Your student record
        • Bayfordbury
        • KASPAR
        • UH Arts

        The small print

        • Terms of use
        • Privacy and cookies
        • Criminal Finances Act 2017
        • Modern Slavery Act 2015
        • Sitemap

        Find/Contact us

        • T: +44 (0)1707 284000
        • E: ask@herts.ac.uk
        • Where to find us
        • Parking
        • hr
        • qaa
        • stonewall
        • AMBA
        • ECU Race Charter
        • disability confident
        • AthenaSwan