Constraining Polarized Foregrounds for EoR Experiments. II. Polarization Leakage Simulations in the Avoidance Scheme
Constraining Polarized Foregrounds for EoR Experiments. II. Polarization Leakage Simulations in the Avoidance Scheme
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DOI：
10.3847/1538-4357/aa8b73
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发表时间：
2017-07
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通讯作者：
C. Nunhokee;G. Bernardi;S. Kohn;J. Aguirre;N. Thyagarajan;J. Dillon;G. Foster;T. Grobler;J. Z. E. Martinot;A. Parsons
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作者：
C. Nunhokee;G. Bernardi;S. Kohn;J. Aguirre;N. Thyagarajan;J. Dillon;G. Foster;T. Grobler;J. Z. E. Martinot;A. Parsons
观测红移21厘米线的一个关键挑战是它与明亮的银河系和河外前景的分离。特别是，极化前景的仪器泄漏，当它们在星际介质中传播时经历了显著的法拉第旋转，可能会有害地污染21厘米的功率谱。对Parsons等人提出的延迟谱方法进行了扩展，提出了一种描述由仪器宽场效应引起的泄漏的公式。我们构建了极化天空模型，并通过仪器模型传播，用精密阵列模拟真实的全天观测，探索再电离时代。我们发现，对于30m的参考基线，在任何k模式下，由于极化点源的数量而引起的泄漏应该比漫射银河系的极化要高。对于相同的参考基线，即使在最悲观的假设下，k>；0.3hMPC−1处的无前景窗口也可以根据漫射星系极化的泄漏来定义。如果给出极化前景功率谱的测量或极化前景的模型，我们的方法能够预测实际21厘米观测中的极化泄漏，潜在地使其能够从测量的21厘米功率谱中统计减去。
A critical challenge in the observation of the redshifted 21 cm line is its separation from bright Galactic and extragalactic foregrounds. In particular, the instrumental leakage of polarized foregrounds, which undergo significant Faraday rotation as they propagate through the interstellar medium, may harmfully contaminate the 21 cm power spectrum. We develop a formalism to describe the leakage due to instrumental widefield effects in visibility-based power spectra measured with redundant arrays, extending the delay-spectrum approach presented in Parsons et al. We construct polarized sky models and propagate them through the instrument model to simulate realistic full-sky observations with the Precision Array to Probe the Epoch of Reionization. We find that the leakage due to a population of polarized point sources is expected to be higher than diffuse Galactic polarization at any k mode for a 30 m reference baseline. For the same reference baseline, a foreground-free window at k > 0.3 h Mpc−1 can be defined in terms of leakage from diffuse Galactic polarization even under the most pessimistic assumptions. If measurements of polarized foreground power spectra or a model of polarized foregrounds are given, our method is able to predict the polarization leakage in actual 21 cm observations, potentially enabling its statistical subtraction from the measured 21 cm power spectrum.