Initial LOFAR observations of epoch of reionization windows II. Diffuse polarized emission in the ELAIS-N1 field
Journal article, 2014
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) data Methods. 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 frequencies Conclusions. 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%.
Dark ages, reionization, first stars
Techniques: interferometric
Cosmology: observations
Techniques: polarimetric
Diffuse radiation
Radio continuum: ISM
Author
V. Jelic
Netherlands Institute for Radio Astronomy (ASTRON)
University of Groningen
A. G. de Bruyn
University of Groningen
Netherlands Institute for Radio Astronomy (ASTRON)
M. Mevius
University of Groningen
F. B. Abdalla
University College London (UCL)
K. M. B. Asad
University of Groningen
G. Bernardi
Square Kilometre Array, South Africa
M. A. Brentjens
Netherlands Institute for Radio Astronomy (ASTRON)
S. Bus
University of Groningen
E. Chapman
University College London (UCL)
B. Ciardi
Max Planck Institute for Astrophysics
S. Daiboo
University of Groningen
E. R. Fernandez
University of Groningen
A. Ghosh
University of Groningen
G. Harker
University of Colorado at Boulder
H. Jensen
Stockholm University
S. Kazemi
University of Groningen
L. V. E. Koopmans
University of Groningen
P. Labropoulos
University of Groningen
O. Martinez-Rubi
University of Groningen
G. Mellema
Stockholm University
A. R. Offringa
ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
Australian National University
V. N. Pandey
Netherlands Institute for Radio Astronomy (ASTRON)
A. H. Patil
University of Groningen
R. M. Thomas
University of Groningen
H. K. Vedantham
University of Groningen
V. Veligatla
University of Groningen
S. Yatawatta
Netherlands Institute for Radio Astronomy (ASTRON)
S. Zaroubi
University of Groningen
A. Alexov
Space Telescope Science Institute (STScI)
J. Anderson
Leibniz Institute for Astrophysics Potsdam
I. M. Avruch
University of Groningen
Netherlands Institute for Space Research (SRON)
R. Beck
Max-Planck Institute for Radio Astronomy
M. E. Bell
ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
M. J. Bentum
Netherlands Institute for Radio Astronomy (ASTRON)
P. Best
University of Edinburgh
A. Bonafede
University of Hamburg
J. Bregman
Netherlands Institute for Radio Astronomy (ASTRON)
F. Breitling
Leibniz Institute for Astrophysics Potsdam
J. Broderick
University of Southampton
W. N. Brouw
University of Groningen
Netherlands Institute for Radio Astronomy (ASTRON)
M. Brueggen
University of Hamburg
H. R. Butcher
Australian National University
John Conway
Chalmers, Earth and Space Sciences, Onsala Space Observatory
F. De Gasperin
University of Hamburg
E. de Geus
Netherlands Institute for Radio Astronomy (ASTRON)
A. Deller
Netherlands Institute for Radio Astronomy (ASTRON)
R. -J. Dettmar
Ruhr-Universität Bochum
S. Duscha
Netherlands Institute for Radio Astronomy (ASTRON)
J. Eislöffel
Thüringer Landessternwarte Tautenburg
D. Engels
Hamburg Observatory
H. Faleke
Netherlands Institute for Radio Astronomy (ASTRON)
Radboud University
R. A. Fallows
Netherlands Institute for Radio Astronomy (ASTRON)
R. Fender
University of Oxford
C. Ferrari
Université Nice Sophia Antipolis (UNS)
W. Frieswijk
Netherlands Institute for Radio Astronomy (ASTRON)
M. A. Garrett
Netherlands Institute for Radio Astronomy (ASTRON)
Leiden University
J. Griessmeier
University of Orléans
Station de Radioastronomie de Nançay
A. W. Gunst
Netherlands Institute for Radio Astronomy (ASTRON)
J. P. Hamaker
Netherlands Institute for Radio Astronomy (ASTRON)
T. E. Hassall
University of Manchester
University of Southampton
M. Haverkorn
Leiden University
Radboud University
G. Heald
Netherlands Institute for Radio Astronomy (ASTRON)
J. W. T. Hessels
Netherlands Institute for Radio Astronomy (ASTRON)
University of Amsterdam
M. Hoeft
Thüringer Landessternwarte Tautenburg
J.R. Hörandel
Radboud University
A. Horneffer
Max-Planck Institute for Radio Astronomy
A. van der Horst
University of Amsterdam
M. Iacobelli
Leiden University
E. Juette
Ruhr-Universität Bochum
A. Karastergiou
University of Oxford
V. I. Kondratiev
Astro Space Center of Lebedev Physical Institute
Netherlands Institute for Radio Astronomy (ASTRON)
M. Kramer
University of Manchester
Max-Planck Institute for Radio Astronomy
M. Kuniyoshi
Max-Planck Institute for Radio Astronomy
G. Kuper
Netherlands Institute for Radio Astronomy (ASTRON)
J. van Leeuwen
University of Amsterdam
Netherlands Institute for Radio Astronomy (ASTRON)
P. Maat
Netherlands Institute for Radio Astronomy (ASTRON)
G. Mann
Leibniz Institute for Astrophysics Potsdam
D. McKay-Bakowski
STFC Rutherford Appleton Laboratory
University of Oulu
J. P. MeKean
University of Groningen
Netherlands Institute for Radio Astronomy (ASTRON)
H. Mank
Netherlands Institute for Radio Astronomy (ASTRON)
A. Nelles
Radboud University
M. J. Morden
Netherlands Institute for Radio Astronomy (ASTRON)
H. Paas
University of Groningen
M. Pandey-Pornmier
Lyon Observatory
G. Pietka
University of Oxford
R. Pizzo
Netherlands Institute for Radio Astronomy (ASTRON)
A. G. Polatidis
Netherlands Institute for Radio Astronomy (ASTRON)
W. Reich
Max-Planck Institute for Radio Astronomy
H. Rottgering
Leiden University
A. Rowlinson
University of Amsterdam
A. M. M. Scaife
University of Southampton
D. Schwarz
Bielefeld University
M. Serylak
University of Oxford
O. Smirnov
Rhodes University
Square Kilometre Array, South Africa
M. Steinmetz
Leibniz Institute for Astrophysics Potsdam
A. Stewart
University of Oxford
M. Tagger
University of Orléans
Y. Tang
Netherlands Institute for Radio Astronomy (ASTRON)
C. Tasse
Observatoire de Paris-Meudon
S. ter Veen
Radboud University
S. Thoudam
Radboud University
C. Toribio
Netherlands Institute for Radio Astronomy (ASTRON)
R. Vermeulen
Netherlands Institute for Radio Astronomy (ASTRON)
C. Voeks
Leibniz Institute for Astrophysics Potsdam
R. J. van Weeren
Harvard-Smithsonian Center for Astrophysics
R. A. M. J. Wijers
University of Amsterdam
S. J. Wijnholds
Netherlands Institute for Radio Astronomy (ASTRON)
O. Wucknitz
Max-Planck Institute for Radio Astronomy
University of Bonn
P. Zarka
Observatoire de Paris-Meudon
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 568 A101Subject Categories
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/201423998