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

V. Jelic; A. G. de Bruyn; M. Mevius; F. B. Abdalla; K. M. B. Asad; G. Bernardi; M. A. Brentjens; S. Bus; E. Chapman; B. Ciardi; S. Daiboo; E. R. Fernandez; A. Ghosh; G. Harker; H. Jensen; S. Kazemi; L. V. E. Koopmans; P. Labropoulos; O. Martinez-Rubi; G. Mellema; A. R. Offringa; V. N. Pandey; A. H. Patil; R. M. Thomas; H. K. Vedantham; V. Veligatla; S. Yatawatta; S. Zaroubi; A. Alexov; J. Anderson; I. M. Avruch; R. Beck; M. E. Bell; M. J. Bentum; P. Best; A. Bonafede; J. Bregman; F. Breitling; J. Broderick; W. N. Brouw; M. Brüggen; H. R. Butcher; J. E. Conway; F. de Gasperin; E. de Geus; A. Deller; R.-J. Dettmar; S. Duscha; J. Eislöffel; D. Engels; H. Falcke; R. A. Fallows; R. Fender; C. Ferrari; W. Frieswijk; M. A. Garrett; J. Grießmeier; A. W. Gunst; J. P. Hamaker; T. E. Hassall; M. Haverkorn; G. Heald; J. W. T. Hessels; M. Hoeft; J. Hörandel; A. Horneffer; A. van der Horst; M. Iacobelli; E. Juette; A. Karastergiou; V. I. Kondratiev; M. Kramer; M. Kuniyoshi; G. Kuper; J. van Leeuwen; P. Maat; G. Mann; D. McKay-Bukowski; J. P. McKean; H. Munk; A. Nelles; M. J. Norden; H. Paas; M. Pandey-Pommier; G. Pietka; R. Pizzo; A. G. Polatidis; W. Reich; H. Röttgering; A. Rowlinson; A. M. M. Scaife; D. Schwarz; M. Serylak; O. Smirnov; M. Steinmetz; A. Stewart; M. Tagger; Y. Tang; C. Tasse; S. ter Veen; S. Thoudam; C. Toribio; R. Vermeulen; C. Vocks; R. J. van Weeren; R. A. M. J. Wijers; S. J. Wijnholds; O. Wucknitz; P. Zarka

doi:10.1051/0004-6361/201423998

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

V. Jelic, A. G. de Bruyn, M. Mevius, F. B. Abdalla, K. M. B. Asad, G. Bernardi, M. A. Brentjens, S. Bus, E. Chapman, B. Ciardi, S. Daiboo, E. R. Fernandez, A. Ghosh, G. Harker, H. Jensen, S. Kazemi, L. V. E. Koopmans, P. Labropoulos, O. Martinez-Rubi, G. MellemaA. R. Offringa, V. N. Pandey, A. H. Patil, R. M. Thomas, H. K. Vedantham, V. Veligatla, S. Yatawatta, S. Zaroubi, A. Alexov, J. Anderson, I. M. Avruch, R. Beck, M. E. Bell, M. J. Bentum, P. Best, A. Bonafede, J. Bregman, F. Breitling, J. Broderick, W. N. Brouw, M. Brüggen, H. R. Butcher, J. E. Conway, F. de Gasperin, E. de Geus, A. Deller, R.-J. Dettmar, S. Duscha, J. Eislöffel, D. Engels, H. Falcke, R. A. Fallows, R. Fender, C. Ferrari, W. Frieswijk, M. A. Garrett, J. Grießmeier, A. W. Gunst, J. P. Hamaker, T. E. Hassall, M. Haverkorn, G. Heald, J. W. T. Hessels, M. Hoeft, J. Hörandel, A. Horneffer, A. van der Horst, M. Iacobelli, E. Juette, A. Karastergiou, V. I. Kondratiev, M. Kramer, M. Kuniyoshi, G. Kuper, J. van Leeuwen, P. Maat, G. Mann, D. McKay-Bukowski, J. P. McKean, H. Munk, A. Nelles, M. J. Norden, H. Paas, M. Pandey-Pommier, G. Pietka, R. Pizzo, A. G. Polatidis, W. Reich, H. Röttgering, A. Rowlinson, A. M. M. Scaife, D. Schwarz, M. Serylak, O. Smirnov, M. Steinmetz, A. Stewart, M. Tagger, Y. Tang, C. Tasse, S. ter Veen, S. Thoudam, C. Toribio, R. Vermeulen, C. Vocks, R. J. van Weeren, R. A. M. J. Wijers, S. J. Wijnholds, O. Wucknitz, P. Zarka

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Abstract

Aims: This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for 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 ~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 ≈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 ~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%.

Original language	English
Journal	Astronomy & astrophysics
Volume	568
DOIs	https://doi.org/10.1051/0004-6361/201423998
Publication status	Published - 1-Aug-2014

Keywords

radio continuum: ISM
techniques: interferometric
techniques: polarimetric
cosmology: observations
diffuse radiation
dark ages
reionization
first stars

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10.1051/0004-6361/201423998

Initial LOFAR observations of epoch of reionizationFinal publisher's version, 28.8 MBLicence: Unspecified

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Jelic, V., de Bruyn, A. G., Mevius, M., Abdalla, F. B., Asad, K. M. B., Bernardi, G., Brentjens, M. A., Bus, S., Chapman, E., Ciardi, B., Daiboo, S., Fernandez, E. R., Ghosh, A., Harker, G., Jensen, H., Kazemi, S., Koopmans, L. V. E., Labropoulos, P., Martinez-Rubi, O., ... 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

@article{78c5d7d84dba404d98a8a275520e1efc,

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

abstract = " Aims: This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for 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 ~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 ≈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 ~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%.",

keywords = "radio continuum: ISM, techniques: interferometric, techniques: polarimetric, cosmology: observations, diffuse radiation, dark ages, reionization, first stars",

author = "V. Jelic and {de Bruyn}, {A. G.} and M. Mevius and Abdalla, {F. B.} and Asad, {K. M. B.} and G. Bernardi and Brentjens, {M. A.} and S. Bus and E. Chapman and B. Ciardi and S. Daiboo and Fernandez, {E. R.} and A. Ghosh and G. Harker and H. Jensen and S. Kazemi and Koopmans, {L. V. E.} and P. Labropoulos and O. Martinez-Rubi and G. Mellema and Offringa, {A. R.} and Pandey, {V. N.} and Patil, {A. H.} and Thomas, {R. M.} and Vedantham, {H. K.} and V. Veligatla and S. Yatawatta and S. Zaroubi and A. Alexov and J. Anderson and Avruch, {I. M.} and R. Beck and Bell, {M. E.} and Bentum, {M. J.} and P. Best and A. Bonafede and J. Bregman and F. Breitling and J. Broderick and Brouw, {W. N.} and M. Br{\"u}ggen and Butcher, {H. R.} and Conway, {J. E.} and {de Gasperin}, F. and {de Geus}, E. and A. Deller and R.-J. Dettmar and S. Duscha and J. Eisl{\"o}ffel and D. Engels and H. Falcke and Fallows, {R. A.} and R. Fender and C. Ferrari and W. Frieswijk and Garrett, {M. A.} and J. Grie{\ss}meier and Gunst, {A. W.} and Hamaker, {J. P.} and Hassall, {T. E.} and M. Haverkorn and G. Heald and Hessels, {J. W. T.} and M. Hoeft and J. H{\"o}randel and A. Horneffer and {van der Horst}, A. and M. Iacobelli and E. Juette and A. Karastergiou and Kondratiev, {V. I.} and M. Kramer and M. Kuniyoshi and G. Kuper and {van Leeuwen}, J. and P. Maat and G. Mann and D. McKay-Bukowski and McKean, {J. P.} and H. Munk and A. Nelles and Norden, {M. J.} and H. Paas and M. Pandey-Pommier and G. Pietka and R. Pizzo and Polatidis, {A. G.} and W. Reich and H. R{\"o}ttgering and A. Rowlinson and Scaife, {A. M. M.} and D. Schwarz and M. Serylak and O. Smirnov and M. Steinmetz and A. Stewart and M. Tagger and Y. Tang and C. Tasse and {ter Veen}, S. and S. Thoudam and C. Toribio and R. Vermeulen and C. Vocks and {van Weeren}, {R. J.} and Wijers, {R. A. M. J.} and Wijnholds, {S. J.} and O. Wucknitz and P. Zarka",

year = "2014",

month = aug,

day = "1",

doi = "10.1051/0004-6361/201423998",

language = "English",

volume = "568",

journal = "Astronomy & astrophysics",

issn = "0004-6361",

publisher = " EDP Sciences",

}

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, G, 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, Brüggen, M, Butcher, HR, Conway, JE, de Gasperin, F, de Geus, E, Deller, A, Dettmar, R-J, Duscha, S, Eislöffel, J, Engels, D, Falcke, 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, Hörandel, 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-Bukowski, D, McKean, JP, Munk, H, Nelles, A, Norden, MJ, Paas, H, Pandey-Pommier, M, Pietka, G, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, 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, Vocks, C, van Weeren, RJ, Wijers, RAMJ, Wijnholds, SJ, Wucknitz, O & Zarka, P 2014, 'Initial LOFAR observations of epoch of reionization windows. II. Diffuse polarized emission in the ELAIS-N1 field', Astronomy & astrophysics, vol. 568. https://doi.org/10.1051/0004-6361/201423998

TY - JOUR

T1 - Initial LOFAR observations of epoch of reionization windows. II. Diffuse polarized emission in the ELAIS-N1 field

AU - Jelic, V.

AU - de Bruyn, A. G.

AU - Mevius, M.

AU - Abdalla, F. B.

AU - Asad, K. M. B.

AU - Bernardi, G.

AU - Brentjens, M. A.

AU - Bus, S.

AU - Chapman, E.

AU - Ciardi, B.

AU - Daiboo, S.

AU - Fernandez, E. R.

AU - Ghosh, A.

AU - Harker, G.

AU - Jensen, H.

AU - Kazemi, S.

AU - Koopmans, L. V. E.

AU - Labropoulos, P.

AU - Martinez-Rubi, O.

AU - Mellema, G.

AU - Offringa, A. R.

AU - Pandey, V. N.

AU - Patil, A. H.

AU - Thomas, R. M.

AU - Vedantham, H. K.

AU - Veligatla, V.

AU - Yatawatta, S.

AU - Zaroubi, S.

AU - Alexov, A.

AU - Anderson, J.

AU - Avruch, I. M.

AU - Beck, R.

AU - Bell, M. E.

AU - Bentum, M. J.

AU - Best, P.

AU - Bonafede, A.

AU - Bregman, J.

AU - Breitling, F.

AU - Broderick, J.

AU - Brouw, W. N.

AU - Brüggen, M.

AU - Butcher, H. R.

AU - Conway, J. E.

AU - de Gasperin, F.

AU - de Geus, E.

AU - Deller, A.

AU - Dettmar, R.-J.

AU - Duscha, S.

AU - Eislöffel, J.

AU - Engels, D.

AU - Falcke, H.

AU - Fallows, R. A.

AU - Fender, R.

AU - Ferrari, C.

AU - Frieswijk, W.

AU - Garrett, M. A.

AU - Grießmeier, J.

AU - Gunst, A. W.

AU - Hamaker, J. P.

AU - Hassall, T. E.

AU - Haverkorn, M.

AU - Heald, G.

AU - Hessels, J. W. T.

AU - Hoeft, M.

AU - Hörandel, J.

AU - Horneffer, A.

AU - van der Horst, A.

AU - Iacobelli, M.

AU - Juette, E.

AU - Karastergiou, A.

AU - Kondratiev, V. I.

AU - Kramer, M.

AU - Kuniyoshi, M.

AU - Kuper, G.

AU - van Leeuwen, J.

AU - Maat, P.

AU - Mann, G.

AU - McKay-Bukowski, D.

AU - McKean, J. P.

AU - Munk, H.

AU - Nelles, A.

AU - Norden, M. J.

AU - Paas, H.

AU - Pandey-Pommier, M.

AU - Pietka, G.

AU - Pizzo, R.

AU - Polatidis, A. G.

AU - Reich, W.

AU - Röttgering, H.

AU - Rowlinson, A.

AU - Scaife, A. M. M.

AU - Schwarz, D.

AU - Serylak, M.

AU - Smirnov, O.

AU - Steinmetz, M.

AU - Stewart, A.

AU - Tagger, M.

AU - Tang, Y.

AU - Tasse, C.

AU - ter Veen, S.

AU - Thoudam, S.

AU - Toribio, C.

AU - Vermeulen, R.

AU - Vocks, C.

AU - van Weeren, R. J.

AU - Wijers, R. A. M. J.

AU - Wijnholds, S. J.

AU - Wucknitz, O.

AU - Zarka, P.

PY - 2014/8/1

Y1 - 2014/8/1

N2 - Aims: This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for 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 ~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 ≈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 ~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%.

AB - Aims: This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for 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 ~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 ≈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 ~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%.

KW - radio continuum: ISM

KW - techniques: interferometric

KW - techniques: polarimetric

KW - cosmology: observations

KW - diffuse radiation

KW - dark ages

KW - reionization

KW - first stars

U2 - 10.1051/0004-6361/201423998

DO - 10.1051/0004-6361/201423998

M3 - Article

SN - 0004-6361

VL - 568

JO - Astronomy & astrophysics

JF - Astronomy & astrophysics

ER -