A 189 MHz, 2400 deg2 POLARIZATION SURVEY WITH THE MURCHISON WIDEFIELD ARRAY 32-ELEMENT PROTOTYPE
A 189 MHz, 2400 deg2 POLARIZATION SURVEY WITH THE MURCHISON WIDEFIELD ARRAY 32-ELEMENT PROTOTYPE
复制标题
使用 Murchison 宽场阵列 32 元件原型进行 189 MHz、2400 deg2 偏振测量
DOI：
10.1088/0004-637x/771/2/105
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
J. Wyithe
中科院分区：
文献类型：
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作者：
G. Bernardi;L. Greenhill;D. Mitchell;S. Ord;B. Hazelton;B. Gaensler;A. D. Oliveira;M. Morales;N. Shankar;R. Subrahmanyan;R. Wayth;E. Lenc;C. Williams;W. Arcus;B. Arora;D. Barnes;J. Bowman;F. Briggs;J. Bunton;R. Cappallo;B. Corey;A. Deshpande;L. deSouza;L. deSouza;D. Emrich;R. Goeke;D. Herne;J. Hewitt;M. Johnston;D. Kaplan;J. Kasper;B. B. Kincaid;R. Koenig;E. Kratzenberg;C. Lonsdale;M. Lynch;S. McWhirter;E. Morgan;D. Oberoi;J. Pathikulangara;T. Prabu;R. Remillard;A. Rogers;A. Roshi;J. Salah;R. Sault;K. Srivani;J. Stevens;S. Tingay;M. Waterson;M. Waterson;R. Webster;A. Whitney;A. R. Williams;J. Wyithe
我们提出了一个斯托克斯我，Q和U调查在189 MHz的默奇森宽场阵列32元件原型覆盖2400 deg 2。测量的角分辨率为15.6弧分，噪声水平为15 mJy beam−1。我们展示了一种新的干涉测量数据分析，涉及漂移扫描数据的校准，通过共同添加的翘曲快照图像的集成，和反卷积的点扩散函数通过正向建模。我们提出了一个点源目录下降到4焦耳的通量限制。我们只从其中一个源（PMN J 0351 -2744）中检测到偏振，其水平为1.8% ± 0.4%，而其余源的偏振分数低于2%。与在1.4 GHz下报道的7%的平均值相比，紧凑源的极化分数在低频下显著降低。我们在大范围的观测中发现了大量的漫射偏振辐射，最大峰值为1013 K，主要是正旋转测量值小于+10 rad m−2。观测到的小值表明，发射可能有一个本地起源（比几百秒差距更近）。在α = 2 h30 m处有一个大的天区，那里的漫射偏振辐射均方根值小于1 K。在这个低银河偏振的区域内，我们用三维功率谱描述了在（α，δ）=（4 h，−27.°6）处冷天空斑块的前景特性。
We present a Stokes I, Q and U survey at 189 MHz with the Murchison Widefield Array 32 element prototype covering 2400 deg2. The survey has a 15.6 arcmin angular resolution and achieves a noise level of 15 mJy beam−1. We demonstrate a novel interferometric data analysis that involves calibration of drift scan data, integration through the co-addition of warped snapshot images, and deconvolution of the point-spread function through forward modeling. We present a point source catalog down to a flux limit of 4 Jy. We detect polarization from only one of the sources, PMN J0351-2744, at a level of 1.8% ± 0.4%, whereas the remaining sources have a polarization fraction below 2%. Compared to a reported average value of 7% at 1.4 GHz, the polarization fraction of compact sources significantly decreases at low frequencies. We find a wealth of diffuse polarized emission across a large area of the survey with a maximum peak of ∼13 K, primarily with positive rotation measure values smaller than +10 rad m−2. The small values observed indicate that the emission is likely to have a local origin (closer than a few hundred parsecs). There is a large sky area at α ⩾ 2h30m where the diffuse polarized emission rms is fainter than 1 K. Within this area of low Galactic polarization we characterize the foreground properties in a cold sky patch at (α, δ) = (4h, −27.°6) in terms of three-dimensional power spectra.