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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
Initial deep LOFAR observations of epoch of reionization windows: I. the north celestial pole
Astronomy and Astrophysics, Volume 550, Article A136, Year 2013
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Description
Aims. The aim of the LOFAR epoch of reionization (EoR) project is to detect the spectral fluctuations of the redshifted HI 21 cm signal. This signal is weaker by several orders of magnitude than the astrophysical foreground signals and hence, in order to achieve this, very long integrations, accurate calibration for stations and ionosphere and reliable foreground removal are essential. Methods. One of the prospective observing windows for the LOFAR EoR project will be centered at the north celestial pole (NCP). We present results from observations of the NCP window using the LOFAR highband antenna (HBA) array in the frequency range 115 MHz to 163 MHz. The data were obtained in April 2011 during the commissioning phase of LOFAR. We used baselines up to about 30 km. The data was processed using a dedicated processing pipeline which is an enhanced version of the standard LOFAR processing pipeline. Results. With about 3 nights, of 6 h each, effective integration we have achieved a noise level of about 100 μJy/PSF in the NCP window. Close to the NCP, the noise level increases to about 180 μJy/PSF, mainly due to additional contamination from unsubtracted nearby sources. We estimate that in our best night, we have reached a noise level only a factor of 1.4 above the thermal limit set by the noise from our Galaxy and the receivers. Our continuum images are several times deeper than have been achieved previously using the WSRT and GMRT arrays. We derive an analytical explanation for the excess noise that we believe to be mainly due to sources at large angular separation from the NCP. We present some details of the data processing challenges and how we solved them. Conclusions. Although many LOFAR stations were, at the time of the observations, in a still poorly calibrated state we have seen no artefacts in our images which would prevent us from producing deeper images in much longer integrations on the NCP window which are about to commence. The limitations present in our current results are mainly due to sidelobe noise from the large number of distant sources, as well as errors related to station beam variations and rapid ionospheric phase fluctuations acting on bright sources. We are confident that we can improve our results with refined processing. © ESO, 2013.
Authors & Co-Authors
Yatawatta, Sarod B.
Netherlands, Groningen
Kapteyn Instituut
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
de Bruyn, A. Ger
Netherlands, Groningen
Kapteyn Instituut
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Brentjens, Michiel A.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Labropoulos, Panagiotis
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Pandey, Vishhambhar N.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Kazemi, Sanaz
Netherlands, Groningen
Kapteyn Instituut
Zaroubi, Saleem
Netherlands, Groningen
Kapteyn Instituut
Koopmans, Léon V.E.
Netherlands, Groningen
Kapteyn Instituut
Offringa, André R.
Netherlands, Groningen
Kapteyn Instituut
Australia, Canberra
Australian National University, Mount Stromlo Observatory
Jelić, Vibor
Netherlands, Groningen
Kapteyn Instituut
Martinez-Rubi, O.
Netherlands, Groningen
Kapteyn Instituut
Veligatla, Vamsikrishna
Netherlands, Groningen
Kapteyn Instituut
Wijnholds, Stefan J.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Brouw, Willem N.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Bernardi, Gianni
Netherlands, Groningen
Kapteyn Instituut
United States, Cambridge
Harvard-smithsonian Center for Astrophysics
Ciardi, Benedetta
Germany, Garching Bei Munchen
Max Planck Institute for Astrophysics
Daiboo, Soobash
Netherlands, Groningen
Kapteyn Instituut
Harker, Geraint J.A.
United States, Boulder
University of Colorado Boulder
Mellema, Garrelt
Sweden, Stockholm
Stockholms Universitet
Schaye, Joop
Netherlands, Leiden
Sterrewacht Leiden
Thomas, Rajat Mani
Netherlands, Groningen
Kapteyn Instituut
Vedantham, Harish K.
Netherlands, Groningen
Kapteyn Instituut
Chapman, Emma
United Kingdom, London
University College London
Abdalla, Fillipe Batoni
United Kingdom, London
University College London
Alexov, Anastasia
United States, Baltimore
Space Telescope Science Institute
Anderson, James M.
Germany, Garching Bei Munchen
Max Planck Institute for Astrophysics
Avruch, Ian Max
Netherlands, Groningen
Kapteyn Instituut
Netherlands, Utrecht
Sron Netherlands Institute for Space Research
Batejat, Fabien
Sweden, Onsala
Onsala Space Observatory
Bell, Martin E.
Australia, Sydney
The University of Sydney
United Kingdom, Southampton
University of Southampton
Bell, Michael R.
Germany, Garching Bei Munchen
Max Planck Institute for Astrophysics
Bentum, Mark J.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Best, Phillip N.
United Kingdom, Edinburgh
Royal Observatory
Bonafede, Annalisa
Germany, Bremen
Constructor University
Bregman, Jaap D.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Breitling, Frank
Germany, Potsdam
Leibniz Institute for Astrophysics Potsdam
van de Brink, R. H.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Broderick, Jess W.
United Kingdom, Southampton
University of Southampton
Brüggen, Marcus
Germany, Bremen
Constructor University
Germany, Hamburg
Universität Hamburg
Conway, John E.
Sweden, Onsala
Onsala Space Observatory
De Gasperin, Francesco
Germany, Hamburg
Universität Hamburg
de Geus, Eugène J.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Duscha, Sven
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Falcke, Heino D.
Netherlands, Nijmegen
Radboud Universiteit
Fallows, Richard A.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Ferrari, Chiara
France, Nice
Laboratoire Joseph-louis Lagrange
Frieswijk, Wilfred W.F.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Garrett, Michael A.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Netherlands, Leiden
Sterrewacht Leiden
Grießmeier, Jean Mathias
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
France, Paris
Cnrs Centre National de la Recherche Scientifique
Gunst, André W.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Hassall, Tom E.
United Kingdom, Southampton
University of Southampton
United Kingdom, Manchester
The University of Manchester
Hessels, Jason W.T.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Netherlands, Amsterdam
Anton Pannekoek Instituut Voor Sterrenkunde
Hoeft, Matthias
Germany, Camburg
Tautenburg Observatory
Iacobelli, Marco
Netherlands, Leiden
Sterrewacht Leiden
Juette, E.
Germany, Bochum
Ruhr-universitat Bochum
Karastergiou, Aris
United Kingdom, Oxford
University of Oxford
Kondratiev, Vladislav I.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Russian Federation, Moscow
P.n. Lebedev Physical Institute of the Russian Academy of Sciences
Kramer, Michael
Germany, Garching Bei Munchen
Max Planck Institute for Astrophysics
United Kingdom, Manchester
The University of Manchester
Kuniyoshi, Masaya
Germany, Garching Bei Munchen
Max Planck Institute for Astrophysics
Kuper, G.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
van Leeuwen, Joeri
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Netherlands, Amsterdam
Anton Pannekoek Instituut Voor Sterrenkunde
Maat, Peter D.H.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Mann, Gottfried J.
Germany, Potsdam
Leibniz Institute for Astrophysics Potsdam
McKean, John P.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Mevius, M.
Netherlands, Groningen
Kapteyn Instituut
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Mol, Jacob David
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Munk, H.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Nijboer, Ronald J.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Noordam, Jan E.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Norden, Menno J.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Orrú, Emanuela
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Netherlands, Nijmegen
Radboud Universiteit
Paas, Harm
Netherlands, Groningen
Rijksuniversiteit Groningen
Pandey-Pommier, Mamta
Netherlands, Leiden
Sterrewacht Leiden
France, Saint-genis-laval
Centre de Recherche Astrophysique de Lyon
Pizzo, Roberto F.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Polatidis, Antonios G.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Reich, Wolfganga
Germany, Garching Bei Munchen
Max Planck Institute for Astrophysics
R̈ottgering, Huub J.A.R.
Netherlands, Leiden
Sterrewacht Leiden
Sluman, J. J.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Smirnov, Oleg M.
South Africa, Grahamstown
Rhodes University
Stappers, Benjamin W.
United Kingdom, Manchester
The University of Manchester
Steinmetz, Matthias
Germany, Potsdam
Leibniz Institute for Astrophysics Potsdam
Tagger, Michel
France, Paris
Cnrs Centre National de la Recherche Scientifique
Tang, Y.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Tasse, Cyril
France, Paris
L'observatoire de Paris
Ter-Veen, Sander
Netherlands, Nijmegen
Radboud Universiteit
Vermeulen, René C.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
van Weeren, Reinout J.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Netherlands, Leiden
Sterrewacht Leiden
United States, Cambridge
Harvard-smithsonian Center for Astrophysics
Wise, Michael W.
Netherlands, Dwingeloo
Netherlands Foundation for Research in Astronomy
Wucknitz, Olaf
Germany, Garching Bei Munchen
Max Planck Institute for Astrophysics
Germany, Bonn
Universität Bonn
Zarka, Philippe M.
France, Paris
L'observatoire de Paris
Statistics
Citations: 89
Authors: 89
Affiliations: 32
Identifiers
Doi:
10.1051/0004-6361/201220874
ISSN:
00046361
e-ISSN:
14320746
Study Design
Cohort Study