2014A&A...568A.101J

Query : 2014A&A...568A.101J

2014A&A...568A.101J - Astronomy and Astrophysics, volume 568A101-101 (2014/8-1)

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

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., MELLEMA G., OFFRINGA A.R., PANDEY V.N., PATIL A.H., THOMAS R.M., VEDANTHAM H.K., VELIGATLA V., YATAWATTA S., ZAROUBI S., ALEXOV A., ANDERSON J., AVRUCH I.M., BECK R., BELL M.E., BENTUM M.J., BEST P., BONAFEDE A., BREGMAN J., BREITLING F., BRODERICK J., BROUW W.N., BRUEGGEN M., BUTCHER H.R., CONWAY J.E., DE GASPERIN F., DE GEUS E., DELLER A., DETTMAR R.-J., DUSCHA S., EISLOEFFEL J., ENGELS D., FALCKE H., FALLOWS R.A., FENDER R., FERRARI C., FRIESWIJK W., GARRETT M.A., GRIESSMEIER J., GUNST A.W., HAMAKER J.P., HASSALL T.E., HAVERKORN M., HEALD G., HESSELS J.W.T., HOEFT M., HOERANDEL J., HORNEFFER A., VAN DER HORST A., IACOBELLI M., JUETTE E., KARASTERGIOU A., KONDRATIEV V.I., KRAMER M., KUNIYOSHI M., KUPER G., VAN LEEUWEN J., MAAT P., MANN G., McKAY-BUKOWSKI D., McKEAN J.P., MUNK H., NELLES A., NORDEN M.J., PAAS H., PANDEY-POMMIER M., PIETKA G., PIZZO R., POLATIDIS A.G., REICH W., ROETTGERING H., ROWLINSON A., SCAIFE A.M.M., 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 R.J., WIJERS R.A.M.J., WIJNHOLDS S.J., WUCKNITZ O. and ZARKA P.

Abstract (from CDS):

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 21cm signal from the LOw-Frequency ARray - Epoch of Reionization (LOFAR-EoR) data. 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. The brightness temperature of the detected Galactic emission is on average ∼4K in polarized intensity and covers the range from -10 to +13rad/m2 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 350MHz 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 150MHz, 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 The wide frequency range, high angular resolution, and high sensitivity make LOFAR an exquisite instrument for studying Galactic polarized emission at a resolution of ∼1-2rad/m2 in Faraday depth. The different polarized patterns observed at 150MHz and 350MHz 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%.

Abstract Copyright: ∼

Journal keyword(s): radio continuum: ISM - techniques: interferometric - techniques: polarimetric - cosmology: observations - diffuse radiation - dark ages, reionization, first stars

Simbad objects: 8

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Number of rows : 8
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 NAME NCP reg 00 00 00 +90 00.0           ~ 216 0
2 3C 196 Sy1 08 13 36.0561170112 +48 13 02.644966020   18.36 17.79     ~ 578 2
3 3C 295 Sy1 14 11 20.6 +52 12 09   22.34 20.80 18.54   ~ 1021 4
4 ELAIS N1 reg 16 10 01 +54 30.6           ~ 489 0
5 Mrk 1498 Sy2 16 28 04.0560946128 +51 46 31.477061100   17.0       ~ 120 1
6 ACO 2255 ClG 17 12 56.0 +64 04 06           ~ 605 0
7 MCG+07-41-003 Bla 19 59 28.35656837 +40 44 02.0972325   16.22 15.10     ~ 2537 2
8 NAME Cas A SNR 23 23 26.0 +58 48 41     14.30     ~ 3033 1

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