Initial LOFAR observations of epoch of reionization windows: II. Diffuse polarized emission in the ELAIS-N1 field
Initial LOFAR observations of epoch of reionization windows: II. Diffuse polarized emission in the ELAIS-N1 field
复制标题
DOI：
10.1051/0004-6361/201423998
复制
发表时间：
2014-07
影响因子：
6.5
通讯作者：
V. Jelić;V. Jelić;A. Bruyn;A. Bruyn;M. Mevius;F. Abdalla;K. Asad;G. Bernardi;M. Brentjens;S. Bus;E. Chapman;B. Ciardi;S. Daiboo;Elizabeth Fernandez;A. Ghosh;G. Harker;H. Jensen;S. Kazemi;L. Koopmans;P. Labropoulos;O. Martinez-Rubi;G. Mellema;A. Offringa;V. Pandey;A. H. Patil;R. Thomas;H. Vedantham;V. Veligatla;S. Yatawatta;S. Zaroubi;A. Alexov;James M. Anderson;I. Avruch;I. Avruch;R. Beck;M. Bell;M. Bentum;P. Best;A. Bonafede;J. Bregman;F. Breitling;J. Broderick;W. Brouw;W. Brouw;M. Brüggen;H. Butcher;J. Conway;F. Gasperin;E. D. Geus;A. Deller;R. Dettmar;S. Duscha;J. Eislöffel;D. Engels;H. Falcke;H. Falcke;R. Fallows;R. Fender;C. Ferrari;W. Frieswijk;M. Garrett;J. Grießmeier;A. Gunst;J. Hamaker;T. Hassall;M. Haverkorn;M. Haverkorn;G. Heald;J. Hessels;M. Hoeft;J. Hörandel;A. Horneffer;A. Horst;M. Iacobelli;E. Juette;A. Karastergiou;V. Kondratiev;M. Kramer;M. Kramer;M. Kuniyoshi;G. Kuper;J. V. Leeuwen;P. Maat;G. Mann;D. McKay-Bukowski;D. McKay-Bukowski;J. McKean;H. Munk;A. Nelles;M. Norden;H. Paas;M. Pandey-Pommier;G. Pietka;R. Pizzo;A. Polatidis;W. Reich;H. Röttgering;A. Rowlinson;A. Scaife;D. Schwarz;M. Serylak;O. Smirnov;M. Steinmetz;A. Stewart;M. Tagger;Y. Tang;C. Tasse;S. Veen;S. Thoudam;C. Toribio;R. Vermeulen;C. Vocks;R. V. Weeren;R. Wijers;S. Wijnholds;O. Wucknitz;O. Wucknitz;P. Zarka
中科院分区：
文献类型：
--
作者：
V. Jelić;V. Jelić;A. Bruyn;A. Bruyn;M. Mevius;F. Abdalla;K. Asad;G. Bernardi;M. Brentjens;S. Bus;E. Chapman;B. Ciardi;S. Daiboo;Elizabeth Fernandez;A. Ghosh;G. Harker;H. Jensen;S. Kazemi;L. Koopmans;P. Labropoulos;O. Martinez-Rubi;G. Mellema;A. Offringa;V. Pandey;A. H. Patil;R. Thomas;H. Vedantham;V. Veligatla;S. Yatawatta;S. Zaroubi;A. Alexov;James M. Anderson;I. Avruch;I. Avruch;R. Beck;M. Bell;M. Bentum;P. Best;A. Bonafede;J. Bregman;F. Breitling;J. Broderick;W. Brouw;W. Brouw;M. Brüggen;H. Butcher;J. Conway;F. Gasperin;E. D. Geus;A. Deller;R. Dettmar;S. Duscha;J. Eislöffel;D. Engels;H. Falcke;H. Falcke;R. Fallows;R. Fender;C. Ferrari;W. Frieswijk;M. Garrett;J. Grießmeier;A. Gunst;J. Hamaker;T. Hassall;M. Haverkorn;M. Haverkorn;G. Heald;J. Hessels;M. Hoeft;J. Hörandel;A. Horneffer;A. Horst;M. Iacobelli;E. Juette;A. Karastergiou;V. Kondratiev;M. Kramer;M. Kramer;M. Kuniyoshi;G. Kuper;J. V. Leeuwen;P. Maat;G. Mann;D. McKay-Bukowski;D. McKay-Bukowski;J. McKean;H. Munk;A. Nelles;M. Norden;H. Paas;M. Pandey-Pommier;G. Pietka;R. Pizzo;A. Polatidis;W. Reich;H. Röttgering;A. Rowlinson;A. Scaife;D. Schwarz;M. Serylak;O. Smirnov;M. Steinmetz;A. Stewart;M. Tagger;Y. Tang;C. Tasse;S. Veen;S. Thoudam;C. Toribio;R. Vermeulen;C. Vocks;R. V. Weeren;R. Wijers;S. Wijnholds;O. Wucknitz;O. Wucknitz;P. Zarka
本研究的目的是在ELAIS-N1领域的偏振前景发射，并解决其可能的影响，从低频阵列-再电离时代（LOFAR-EoR）数据的宇宙学21厘米信号的提取。我们使用LOFAR的高波段天线来成像这个区域，并使用RM合成来解开银河系高纬度极化发射的结构。探测到的银河系辐射的亮温平均为4 K，偏振强度在法拉第深度范围为-10至+13 rad m^-2。总偏振强度和偏振角显示出广泛的形态特征。我们还使用了韦斯特博克综合射电望远镜（WSRT）在350兆赫的图像相同的区域。LOFAR和WSRT图像显示出相似的复杂形态，在可比的亮度水平，但它们的空间相关性非常低。在150 MHz的分数极化，表示为总强度的百分比，相当于1.5%。在干涉测量数据中，总强度中没有漫发射的迹象，这与较高频率下的结果一致。LOFAR具有宽的频率范围、良好的角分辨率和灵敏度，是研究银河系偏振辐射的一种精密仪器，在法拉第深度上的分辨率为1-2 rad/m^-2。在150 MHz和350 MHz下观察到的不同极化图案与在各种法拉第薄发射区域中沿沿着视线扭曲的不同源分布一致。极化前景的存在是再电离时代实验的一个严重并发症。为了避免偏振发射泄漏到总强度中（这可能取决于频率），我们需要将整个视场的仪器偏振校准到1%的小部分。
This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for the extraction of the cosmological 21-cm signal from the Low-Frequency Array - Epoch of Reionization (LOFAR-EoR) data. We use 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 4 K in polarized intensity and covers the range from -10 to +13rad 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. The wide frequency range, good angular resolution and good 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 polarised 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 polarised 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%.