Removing systematics-induced 21-cm foreground residuals by cross-correlating filtered data
Removing systematics-induced 21-cm foreground residuals by cross-correlating filtered data
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DOI：
10.1103/physrevd.106.043534
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发表时间：
2022-03
影响因子：
5
通讯作者：
Haochen Wang;J. Mena-Parra;Tianyue Chen;K. Masui
中科院分区：
文献类型：
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作者：
Haochen Wang;J. Mena-Parra;Tianyue Chen;K. Masui
对中性氢发出的红移21厘米信号的观测表明，这是一个很有希望的宇宙大规模结构探测器。然而，由于天体物理前景要亮几个数量级，宇宙21厘米信号的观测具有挑战性。传统的线性前景去除方法可以最优地去除已知望远镜响应的前景，但对诸如天线增益和延迟误差的望远镜系统误差敏感，在恢复的信号中留下前景污染。另一方面，诸如主成分分析之类的非线性方法已被成功地用于前景去除，但它们会导致难以表征且需要仔细分析的信号损失。在本文中，我们提出了一种结合线性和非线性方法的系统稳健的前景去除技术。我们首先使用线性滤波获得信号和前景估计。在假设信号估计被可参数化系统效应引起的前景残差污染的假设下，我们通过将初始信号和前景估计互相关来推断系统引起的污染。对推断的误差进行校正，我们能够从线性滤波的信号中减去前景污染，直到望远镜系统的幅度的一阶。在对21厘米干涉测量的模拟中，我们的算法将功率谱中由复增益误差引起的前景泄漏消除了一到两个数量级。因此，我们的技术简化了现代和下一代21厘米宇宙学实验对望远镜特性的要求。
Observations of the redshifted 21-cm signal emitted by neutral hydrogen represent a promising probe of large-scale structure in the universe. However, cosmological 21-cm signal is challenging to observe due to astrophysical foregrounds which are several orders of magnitude brighter. Traditional linear foreground removal methods can optimally remove foregrounds for a known telescope response but are sensitive to telescope systematic errors such as antenna gain and delay errors, leaving foreground contamination in the recovered signal. Non-linear methods such as principal component analysis, on the other hand, have been used successfully for foreground removal, but they lead to signal loss that is difficult to characterize and requires careful analysis. In this paper, we present a systematics-robust foreground removal technique which combines both linear and non-linear methods. We first obtain signal and foreground estimates using a linear filter. Under the assumption that the signal estimate is contaminated by foreground residuals induced by parameterizable systematic effects, we infer the systematics-induced contamination by cross-correlating the initial signal and foreground estimates. Correcting for the inferred error, we are able to subtract foreground contamination from the linearly filtered signal up to the first order in the amplitude of the telescope systematics. In simulations of an interferometric 21-cm survey, our algorithm removes foreground leakage induced by complex gain errors by one to two orders of magnitude in the power spectrum. Our technique thus eases the requirements on telescope characterization for modern and next-generation 21-cm cosmology experiments.