Initial LOFAR observations of epoch of reionization windows II. Diffuse polarized emission in the ELAIS-N1 field

Jelic V, De Bruyn AG, Mevius M, Abdalla FB, Asad KMB, Bernardi G, Brentjens MA, Bus S, Chapman E, Ciardi B, Daiboo S, Fernandez ER, Ghosh A, Harker GJ, Jensen H, Kazemi S, Koopmans LVE, Labropoulos P, Martinez-Rubi O, Mellema G, Offringa AR, Pandey VN, Patil AH, Thomas RM, Vedantham HK, Veligatla V, Yatawatta S, Zaroubi S, Alexov A, Anderson J, Avruch IM, Beck R, Bell ME, Bentum MJ, Best P, Bonafede A, Bregman J, Breitling F, Broderick J, Brouw WN, Brueggen M, Butcher HR, Conway JE, De Gasperin F, De Geus E, Deller A, Dettmar RJ, Duscha S, Eisloeffel J, Engels D, Faleke H, Fallows RA, Fender R, Ferrari C, Frieswijk W, Garrett MA, Griessmeier J, Gunst AW, Hamaker JP, Hassall TE, Haverkorn M, Heald G, Hessels JWT, Hoeft M, Hoerandel J, Horneffer A, Van Der Horst A, Iacobelli M, Juette E, Karastergiou A, Kondratiev VI, Kramer M, Kuniyoshi M, Kuper G, Van Leeuwen J, Maat P, Mann G, Mckay-Bakowski D, Mekean JP, Mank H, Nelles A, Morden MJ, Paas H, Pandey-Pornmier M, Pietka G, Pizzo R, Polatidis AG, Reich W, Roettgering H, Rowlinson A, Scaife AMM, Schwarz D, Serylak M, Smirnov O, Steinmetz M, Stewart A, Tagger M, Tang Y, Tasse C, Ter Veen S, Thoudam S, Toribio C, Vermeulen R, Voeks C, Van Weeren RJ, Wijers RAMJ, Wijnholds SJ, Wucknitz O, Zarka P (2014)

Publication Status: Published

Publication Type: Journal article

Publication year: 2014

Journal

Publisher: EDP SCIENCES S A

Book Volume: 568

Article Number: ARTN A101

DOI: 10.1051/0004-6361/201423998

Abstract

Aims. This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications or extracting of the cosmological 21 cm signal from the LOw-Frequency ARray - Epoch of Reionization (LOFAR-EoR) dataMethods. We used the high band antennas of LOFAR to image this region and RM-synthesis to unravel structures of polarized emission at high Galactic latitudes.Results. The brightness temperature of the detected Galactic emission is on average similar to 4 K in polarized intensity and covers the range from -10 to +13 rad m(-2) in Faraday depth, The total polarized intensity and polarization angle show a wide range of morphological features. We have also used the Westerbork Synthesis Radio Telescope (WSRT) at 350 MHz to image the same region. The LOFAR and WSRT images show a similar complex morphology at comparable brightness levels, but their spatial correlation is very low. The fractional polarization at 150 MHz, expressed as a percentage of the total intensity, amounts to approximate to 1.5%. There is no indication of diffuse emission in total intensity in the interferometric data. in line with results at higher frequenciesConclusions. The wide frequency range. high angular resolution, and high sensitivity make LOFAR an exquisite instrument for studying Galactic polarized emission at a resolution of similar to 1-2 rad m(-2) in Faraday depth. The different polarized patterns observed at 150 MHz and 350 MHz are consistent with different source distributions along the line of sight wring in a variety of Faraday thin regions of emission. The presence of polarized foregrounds is a serious complication for epoch of reionization experiments. To avoid the leakage of polarized emission into total intensity, which can depend on frequency, we need to calibrate the instrumental polarization across the field of view to a small fraction of 1%.

Authors with CRIS profile

Involved external institutions

Astron Netherlands (NL) Universität Hamburg (UHH) Germany (DE) Max-Planck-Institut für Radioastronomie / Max Planck Institute for Radio Astronomy Germany (DE) University of Edinburgh United Kingdom (GB) Universität Bielefeld Germany (DE) Leiden University Netherlands (NL) University of Southampton United Kingdom (GB) University of Groningen / Rijksuniversiteit Groningen Netherlands (NL) Observatoire de Lyon France (FR) SKA South Africa South Africa (ZA) University of Oxford United Kingdom (GB) University of Amsterdam Netherlands (NL) Radboud University Nijmegen Netherlands (NL) Ruhr-Universität Bochum (RUB) Germany (DE) Stockholm University / Stockholms universitet Sweden (SE) Oulun Yliopisto / University of Oulo Finland (FI) University of Orléans / Université d'Orléans France (FR) Chalmers University of Technology / Chalmers tekniska högskola Sweden (SE) Leibniz Institute for Astrophysics Potsdam / Leibniz-Institut für Astrophysik Potsdam Germany (DE) Australian National University (ANU) Australia (AU) Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. (MPG) / Max Planck Society for the Advancement of Science Germany (DE) University of Colorado at Boulder United States (USA) (US) PSL Research University / Université de recherche Paris Sciences et Lettres France (FR) University College London (UCL) United Kingdom (GB) Thüringer Landessternwarte Tautenburg (TLS) - Karl-Schwarzschild-Observatorium Germany (DE) ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO) Australia (AU) Harvard University United States (USA) (US) University of Nice Sophia Antipolis / Université Nice Sophia Antipolis France (FR) Space Telescope Science Institute (STScI) United States (USA) (US)

How to cite

APA:

Jelic, V., De Bruyn, A.G., Mevius, M., Abdalla, F.B., Asad, K.M.B., Bernardi, G.,... Zarka, P. (2014). Initial LOFAR observations of epoch of reionization windows II. Diffuse polarized emission in the ELAIS-N1 field. Astronomy & Astrophysics, 568. https://doi.org/10.1051/0004-6361/201423998

MLA:

Jelic, Vibor, et al. "Initial LOFAR observations of epoch of reionization windows II. Diffuse polarized emission in the ELAIS-N1 field." Astronomy & Astrophysics 568 (2014).

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