Initial deep LOFAR observations of epoch of reionization windows I. The north celestial pole

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MARC

Yatawatta, S.Netherlands Institute for Radio Astronomy (ASTRON),Rijksuniversiteit Groningen,University of Groningen (author)

Initial deep LOFAR observations of epoch of reionization windows I. The north celestial pole

Article/chapterEnglish2013

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2013-02-07
EDP Sciences,2013
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LIBRIS-ID:oai:DiVA.org:su-88739
https://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-88739URI
https://doi.org/10.1051/0004-6361/201220874DOI
https://research.chalmers.se/publication/174893URI

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Language:English
Summary in:English

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SwePubSwePub

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Subject category:ref swepub-contenttype
Subject category:art swepub-publicationtype

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AuthorCount:89;
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 mu Jy/PSF in the NCP window. Close to the NCP, the noise level increases to about 180 mu Jy/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.

Subject headings and genre

NATURVETENSKAP Fysik Astronomi, astrofysik och kosmologi hsv//swe
NATURAL SCIENCES Physical Sciences Astronomy, Astrophysics and Cosmology hsv//eng
dark ages
reionization
first stars
instrumentation: interferometers
techniques: interferometric
methods: data analysis

Added entries (persons, corporate bodies, meetings, titles ...)

de Bruyn, A. G.Rijksuniversiteit Groningen,University of Groningen,Netherlands Institute for Radio Astronomy (ASTRON),Space Telescope Science Institute (STScI) (author)
Brentjens, M. A.Netherlands Institute for Radio Astronomy (ASTRON),Rijksuniversiteit Groningen,University of Groningen (author)
Labropoulos, P.Netherlands Institute for Radio Astronomy (ASTRON) (author)
Pandey, V. N.Netherlands Institute for Radio Astronomy (ASTRON),Rijksuniversiteit Groningen,University of Groningen (author)
Kazemi, S.Rijksuniversiteit Groningen,University of Groningen (author)
Zaroubi, S.Rijksuniversiteit Groningen,University of Groningen (author)
Koopmans, L. V. E.Rijksuniversiteit Groningen,University of Groningen (author)
Offringa, A. R.Rijksuniversiteit Groningen,University of Groningen,Mount Stromlo Observatory (author)
Jelic, V.Rijksuniversiteit Groningen,University of Groningen,Netherlands Institute for Radio Astronomy (ASTRON),Universiteit Van Amsterdam,University of Amsterdam,Harvard-Smithsonian Center for Astrophysics,Universiteit Leiden (UL),Leiden University (UL) (author)
Rubi, O. MartinezRijksuniversiteit Groningen,University of Groningen (author)
Veligatla, V.Netherlands Institute for Radio Astronomy (ASTRON),Astro Space Center of Lebedev Physical Institute (author)
Wijnholds, S. J.Netherlands Institute for Radio Astronomy (ASTRON),Universiteit Leiden (UL),Leiden University (UL) (author)
Brouw, W. N.Netherlands Institute for Radio Astronomy (ASTRON) (author)
Bernardi, G.Harvard-Smithsonian Center for Astrophysics,Rijksuniversiteit Groningen,University of Groningen (author)
Ciardi, B.Max-Planck-Institut für Astrophysik,Max Planck Institute for Astrophysics (author)
Daiboo, S.Rijksuniversiteit Groningen,University of Groningen (author)
Harker, G.University of Colorado at Boulder (author)
Mellema, GarreltStockholms universitet,Institutionen för astronomi,Oskar Klein-centrum för kosmopartikelfysik (OKC),Stockholm University,Universiteit Leiden (UL),Leiden University (UL),Netherlands Institute for Radio Astronomy (ASTRON)(Swepub:su)gmell (author)
Schaye, J. (author)
Thomas, R.Rijksuniversiteit Groningen,University of Groningen (author)
Vedantham, H.Rijksuniversiteit Groningen,University of Groningen (author)
Chapman, E.University College London (UCL) (author)
Batejat, Fabien,1979University College London (UCL),Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)em1fabat (author)
Alexov, A.Netherlands Institute for Radio Astronomy (ASTRON),University Of Oxford (author)
Anderson, J.Max-Planck-Institut für Astrophysik,Max Planck Institute for Astrophysics (author)
Avruch, I. M.Netherlands Institute for Space Research (SRON),Rijksuniversiteit Groningen,University of Groningen,Universiteit Leiden (UL),Leiden University (UL) (author)
Batejat, F. (author)
Bell, M. E.University of Southampton,The University of Sydney (author)
Bell, M. R.Max-Planck-Institut für Astrophysik,Max Planck Institute for Astrophysics (author)
Bentum, M.Netherlands Institute for Radio Astronomy (ASTRON) (author)
Best, P.Royal Observatory (author)
Bonafede, A. (author)
Bregman, J.Netherlands Institute for Radio Astronomy (ASTRON) (author)
Breitling, F.Leibniz-Institut Für Astrophysik Potsdam,Leibniz Institute for Astrophysics Potsdam (author)
van de Brink, R. H.Netherlands Institute for Radio Astronomy (ASTRON),Universiteit Leiden (UL),Leiden University (UL) (author)
Broderick, J. W.University of Southampton (author)
Brueggen, M.Universität Hamburg,University of Hamburg (author)
Conway, John,1963Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)jconway (author)
de Gasperin, F.Universität Hamburg,University of Hamburg (author)
de Geus, E.Netherlands Institute for Radio Astronomy (ASTRON) (author)
Duscha, S.Netherlands Institute for Radio Astronomy (ASTRON) (author)
Falcke, H.Radboud Universiteit,Radboud University (author)
Fallows, R. A. (author)
Ferrari, C.Université Nice Sophia Antipolis (UNS) (author)
Frieswijk, W.Netherlands Institute for Radio Astronomy (ASTRON) (author)
Garrett, M. A.Leibniz-Institut Für Astrophysik Potsdam,Leibniz Institute for Astrophysics Potsdam (author)
Griessmeier, J. M.Centre national de la recherche scientifique (CNRS),Netherlands Institute for Radio Astronomy (ASTRON) (author)
Gunst, A. W. (author)
Hassall, T. E.University of Manchester,University of Southampton (author)
Hessels, J. W. T.Netherlands Institute for Radio Astronomy (ASTRON),Universiteit Van Amsterdam,University of Amsterdam (author)
Hoeft, M.Thüringer Landessternwarte Tautenburg,Netherlands Institute for Radio Astronomy (ASTRON) (author)
Iacobelli, M. (author)
Juette, E.Ruhr-Universität Bochum,Netherlands Institute for Radio Astronomy (ASTRON) (author)
Karastergiou, A. (author)
Kondratiev, V. I. (author)
Kramer, M.University of Manchester,Max-Planck-Institut für Astrophysik,Max Planck Institute for Astrophysics (author)
Kuniyoshi, M.Max-Planck-Institut für Astrophysik,Max Planck Institute for Astrophysics (author)
Kuper, G.Netherlands Institute for Radio Astronomy (ASTRON) (author)
van Leeuwen, J. (author)
Maat, P.Netherlands Institute for Radio Astronomy (ASTRON),Universiteit Leiden (UL),Leiden University (UL),Observatoire de Lyon,Lyon Observatory (author)
Mann, G. (author)
McKean, J. P.Netherlands Institute for Radio Astronomy (ASTRON) (author)
Mevius, M.Netherlands Institute for Radio Astronomy (ASTRON),Leibniz-Institut Für Astrophysik Potsdam,Leibniz Institute for Astrophysics Potsdam,Centre national de la recherche scientifique (CNRS) (author)
Mol, J. D.Netherlands Institute for Radio Astronomy (ASTRON) (author)
Munk, H. (author)
Nijboer, R.Netherlands Institute for Radio Astronomy (ASTRON) (author)
Noordam, J. E. (author)
Norden, M. J. (author)
Orru, E.Radboud Universiteit,Radboud University,Netherlands Institute for Radio Astronomy (ASTRON) (author)
Paas, H.Rijksuniversiteit Groningen,University of Groningen (author)
Pandey-Pommier, M. (author)
Pizzo, R.Netherlands Institute for Radio Astronomy (ASTRON) (author)
Polatidis, A. G. (author)
Reich, W.Max-Planck-Institut für Astrophysik,Max Planck Institute for Astrophysics (author)
Rottgering, H. J. A. (author)
Sluman, J. (author)
Smirnov, O.Rhodes University (author)
Stappers, B.University of Manchester (author)
Steinmetz, M. (author)
Tagger, M. (author)
Tang, Y.Netherlands Institute for Radio Astronomy (ASTRON) (author)
Tasse, C.Observatoire de Paris-Meudon (author)
ter Veen, S.Radboud Universiteit,Radboud University (author)
Vermeulen, R.Netherlands Institute for Radio Astronomy (ASTRON) (author)
van Weeren, R. J. (author)
Wise, M. (author)
Wucknitz, O.Max-Planck-Institut für Astrophysik,Max Planck Institute for Astrophysics (author)
Zarka, P.Observatoire de Paris-Meudon (author)
Netherlands Institute for Radio Astronomy (ASTRON)Rijksuniversiteit Groningen (creator_code:org_t)

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By the author/editor: Yatawatta, S.; de Bruyn, A. G.; Brentjens, M. A.; Labropoulos, P.; Pandey, V. N.; Kazemi, S.; show more...; Zaroubi, S.; Koopmans, L. V. ...; Offringa, A. R.; Jelic, V.; Rubi, O. Martine ...; Veligatla, V.; Wijnholds, S. J.; Brouw, W. N.; Bernardi, G.; Ciardi, B.; Daiboo, S.; Harker, G.; Mellema, Garrelt; Schaye, J.; Thomas, R.; Vedantham, H.; Chapman, E.; Batejat, Fabien, ...; Alexov, A.; Anderson, J.; Avruch, I. M.; Batejat, F.; Bell, M. E.; Bell, M. R.; Bentum, M.; Best, P.; Bonafede, A.; Bregman, J.; Breitling, F.; van de Brink, R. ...; Broderick, J. W.; Brueggen, M.; Conway, John, 19 ...; de Gasperin, F.; de Geus, E.; Duscha, S.; Falcke, H.; Fallows, R. A.; Ferrari, C.; Frieswijk, W.; Garrett, M. A.; Griessmeier, J. ...; Gunst, A. W.; Hassall, T. E.; Hessels, J. W. T ...; Hoeft, M.; Iacobelli, M.; Juette, E.; Karastergiou, A.; Kondratiev, V. I ...; Kramer, M.; Kuniyoshi, M.; Kuper, G.; van Leeuwen, J.; Maat, P.; Mann, G.; McKean, J. P.; Mevius, M.; Mol, J. D.; Munk, H.; Nijboer, R.; Noordam, J. E.; Norden, M. J.; Orru, E.; Paas, H.; Pandey-Pommier, ...; Pizzo, R.; Polatidis, A. G.; Reich, W.; Rottgering, H. J ...; Sluman, J.; Smirnov, O.; Stappers, B.; Steinmetz, M.; Tagger, M.; Tang, Y.; Tasse, C.; ter Veen, S.; Vermeulen, R.; van Weeren, R. J ...; Wise, M.; Wucknitz, O.; Zarka, P.; show less...

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