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

被引：75

作者：

Jelic, V. ^{[1
,2
]}

de Bruyn, A. G. ^{[1
,2
]}

Mevius, M. ^{[1
]}

Abdalla, F. B. ^{[3
]}

Asad, K. M. B. ^{[1
]}

Bernardi, G. ^{[4
]}

Brentjens, M. A. ^{[2
]}

Bus, S. ^{[1
]}

Chapman, E. ^{[3
]}

Ciardi, B. ^{[5
]}

Daiboo, S. ^{[1
]}

Fernandez, E. R. ^{[1
]}

Ghosh, A. ^{[1
]}

Harker, G. ^{[6
]}

Jensen, H. ^{[7
,8
]}

Kazemi, S. ^{[1
]}

Koopmans, L. V. E. ^{[1
]}

Labropoulos, P. ^{[1
]}

Martinez-Rubi, O. ^{[1
]}

Mellema, G. ^{[7
,8
]}

Offringa, A. R. ^{[9
,10
]}

Pandey, V. N. ^{[2
]}

Patil, A. H. ^{[1
]}

Thomas, R. M. ^{[1
]}

Vedantham, H. K. ^{[1
]}

Veligatla, V. ^{[1
]}

Yatawatta, S. ^{[2
]}

Zaroubi, S. ^{[1
]}

Alexov, A. ^{[11
]}

Anderson, J. ^{[12
]}

Avruch, I. M. ^{[1
,13
]}

Beck, R. ^{[14
]}

Bell, M. E. ^{[10
]}

Bentum, M. J. ^{[2
]}

Best, P. ^{[15
]}

Bonafede, A. ^{[16
]}

Bregman, J. ^{[2
]}

Breitling, F. ^{[12
]}

Broderick, J. ^{[17
]}

Brouw, W. N. ^{[1
,2
]}

Brueggen, M. ^{[16
]}

Butcher, H. R. ^{[9
]}

Conway, J. E. ^{[18
]}

de Gasperin, F. ^{[16
]}

de Geus, E. ^{[2
]}

Deller, A. ^{[2
]}

Dettmar, R. -J. ^{[19
]}

Duscha, S. ^{[2
]}

Eisloeffel, J. ^{[20
]}

Engels, D. ^{[21
]}

机构：

[1] Univ Groningen, Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands

[2] ASTRON, NL-7990 AA Dwingeloo, Netherlands

[3] UCL, Dept Phys & Astron, London WC1E 6BT, England

[4] SKA SA, ZA-7405 Pinelands, South Africa

[5] Max Planck Inst Astrophys, D-85748 Garching, Germany

[6] 389 Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA

[7] Stockholm Univ, Dept Astron, S-10691 Stockholm, Sweden

[8] Stockholm Univ, Oskar Klein Ctr, S-10691 Stockholm, Sweden

[9] Australian Natl Univ, RSAA, Mt Stromlo Observ, Weston, ACT 2611, Australia

[10] ARC Ctr Excellence All Sky Astrophys CAASTRO, Sydney, NSW, Australia

[11] Space Telescope Sci Inst, Baltimore, MD 21218 USA

[12] Leibniz Inst Astrophys Potsdam AIP, D-14482 Potsdam, Germany

[13] SRON Netherlands Inst Space Res, NL-9700 AV Groningen, Netherlands

[14] Max Planck Inst Radioastron, D-53121 Bonn, Germany

[15] Univ Edinburgh, Inst Astron, Royal Observ Edinburgh, Edinburgh EH9 3HJ, Midlothian, Scotland

[16] Univ Hamburg, D-21029 Hamburg, Germany

[17] Univ Southampton, Sch Phys & Astron, Southampton SO17 1BJ, Hants, England

[18] Chalmers, Dept Earth & Space Sci, Onsala Space Observ, S-43992 Onsala, Sweden

[19] Ruhr Univ Bochum, Astron Inst, D-44780 Bochum, Germany

[20] Thuringer Landessterwarte, D-07778 Tautenburg, Germany

[21] Hamburger Sternwarte, D-21029 Hamburg, Germany

[22] Radboud Univ Nijmegen, Dept Astrophys IMAPP, NL-6500 GL Nijmegen, Netherlands

[23] Univ Oxford, Oxford OX1 3RH, England

[24] Univ Nice Sophia Antipolis, Lab Lagrange, UMR7293, CNRS,Observ Cote Azur, F-06300 Nice, France

[25] Leiden Univ, Leiden Observ, NL-2300 RA Leiden, Netherlands

[26] Univ Orleans, CNRS, LPC2E, Orleans, France

[27] Univ Orleans, Stn Radioastron Nancay, Observ Paris, CNRS,INSU,USR 704,OSUC, F-18330 Nancay, France

[28] Univ Manchester, Sch Phys & Astron, Jodrell Bank Ctr Astrophys, Manchester M13 9PL, Lancs, England

[29] Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1090 GE Amsterdam, Netherlands

[30] Lebedev Phys Inst, Ctr Astro Space, Moscow 117997, Russia

[31] Univ Oulu, Sodankyla Geophys Observ, Sodankyla 99600, Finland

[32] STFC Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England

[33] Univ Groningen, Ctr Informat Technol, NL-9700 AB Groningen, Netherlands

[34] Observ Lyon, Ctr Rech Astrophys Lyon, F-69561 St Genis Laval, France

[35] Univ Bielefeld, Fak Phys, D-33501 Bielefeld, Germany

[36] Rhodes Univ, Dept Phys & Elect, ZA-6140 Grahamstown, South Africa

[37] Observ Paris, CNRS, LESIA, UMR 8109, F-92195 Meudon, France

[38] Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA

[39] Univ Bonn, Argelander Inst Astron, D-53121 Bonn, Germany

来源：

ASTRONOMY & ASTROPHYSICS | 2014年 / 568卷

关键词：

radio continuum: ISM; techniques: interferometric; techniques: polarimetric; cosmology: observations; diffuse radiation; dark ages; reionization; first stars; ROTATION MEASURE SYNTHESIS; NORTH CELESTIAL POLE; 350; MHZ; MULTIFREQUENCY POLARIMETRY; FOREGROUND REMOVAL; GALACTIC EMISSION; SELF-CALIBRATION; WIDE-FIELD; SKY SURVEY; RADIO;

D O I：

10.1051/0004-6361/201423998

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

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%.

引用

页数：12

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