红移21厘米功率谱干涉测量中的前景污染
Foreground Contamination in Interferometric Measurements of the Redshifted 21 cm Power Spectrum
摘要：
从默奇森宽场阵列（MWA）的模拟测量产生的“脏”的天空地图中减去天体物理前景污染已通过拟合沿数据立方体中的每个像素的光谱维度的三阶多项式来执行。模拟是第一个包括不可避免的仪器效应的频率依赖的主天线波束和合成阵列波束。他们将一维球面元输入的红移21 cm功率谱恢复到MWA最灵敏探测尺度（0.01 < k < 1 Mpc^-1）的约1%以内，并证明了真实的仪器效应不会掩盖EoR信号。我们发现，加权函数用于产生脏天空地图的网格能见度测量是重要的技术的成功。能见度测量的均匀加权产生最好的结果，而自然加权通过将能见度测量的密度中的结构耦合到脏天空图数据立方体中的光谱结构来显著地消除前景减法。发现MWA的极其密集的UV覆盖对于该技术是有利的，并且在对应于UV平面中的|u| < 500波长的尺度上产生非常好的结果，而无需对UV覆盖进行任何选择性编辑。
英文摘要：
Subtraction of astrophysical foreground contamination from "dirty" sky maps produced by simulated measurements of the Murchison Widefield Array (MWA) has been performed by fitting a 3rd-order polynomial along the spectral dimension of each pixel in the data cubes. The simulations are the first to include the unavoidable instrumental effects of the frequency-dependent primary antenna beams and synthesized array beams. They recover the one-dimensional spherically-binned input redshifted 21 cm power spectrum to within approximately 1% over the scales probed most sensitively by the MWA (0.01 < k < 1 Mpc^-1) and demonstrate that realistic instrumental effects will not mask the EoR signal. We find that the weighting function used to produce the dirty sky maps from the gridded visibility measurements is important to the success of the technique. Uniform weighting of the visibility measurements produces the best results, whereas natural weighting significantly worsens the foreground subtraction by coupling structure in the density of the visibility measurements to spectral structure in the dirty sky map data cube. The extremely dense uv-coverage of the MWA was found to be advantageous for this technique and produced very good results on scales corresponding to |u| < 500 wavelengths in the uv-plane without any selective editing of the uv-coverage.
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