Precise instrumental calibration is of crucial importance to 21-cm cosmology experiments. The Murchison Widefield Array’s (MWA) Phase II compact configuration offers us opportunities for both redundant calibration and sky-based calibration algorithms; using the two in tandem is a potential approach to mitigate calibration errors caused by inaccurate sky models. The MWA Epoch of Reionization (EoR) experiment targets three patches of the sky (dubbed EoR0, EoR1, and EoR2) with deep observations. Previous work in Li et al. (2018) and (2019) studied the effect of tandem calibration on the EoR0 field and found that it yielded no significant improvement in the power spectrum (PS) over sky-based calibration alone. In this work, we apply similar techniques to the EoR1 field and find a distinct result: the improvements in the PS from tandem calibration are significant. To understand this result, we analyse both the calibration solutions themselves and the effects on the PS over three nights of EoR1 observations. We conclude that the presence of the bright radio galaxy Fornax A in EoR1 degrades the performance of sky-based calibration, which in turn enables redundant calibration to have a larger impact. These results suggest that redundant calibration can indeed mitigate some level of model incompleteness error.

中文翻译：

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串联冗余/基于天空的校准在 MWA 第二阶段数据分析中的影响

精确的仪器校准对于 21 厘米宇宙学实验至关重要。Murchison 宽场阵列 (MWA) Phase II 紧凑型配置为我们提供了冗余校准和基于天空的校准算法的机会；将两者结合使用是减轻由不准确的天空模型引起的校准误差的一种潜在方法。MWA 再电离时代 (EoR) 实验针对三个天空区域（称为 EoR0、EoR1 和 EoR2）进行深度观测。Li等人以前的工作。(2018) 和 (2019) 研究了串联校准对 EoR0 场的影响，发现与单独的基于天空的校准相比，它在功率谱 (PS) 方面没有显着改善。在这项工作中，我们将类似的技术应用于 EoR1 领域并发现了一个明显的结果：串联校准对 PS 的改进是显着的。为了理解这个结果，我们分析了校准解决方案本身以及在三个晚上的 EoR1 观测中对 PS 的影响。我们得出结论，EoR1 中明亮的射电星系 Fornax A 的存在降低了基于天空的校准的性能，这反过来又使冗余校准产生了更大的影响。这些结果表明，冗余校准确实可以减轻某种程度的模型不完整性误差。这反过来又使冗余校准产生更大的影响。这些结果表明，冗余校准确实可以减轻某种程度的模型不完整性误差。这反过来又使冗余校准产生更大的影响。这些结果表明，冗余校准确实可以减轻某种程度的模型不完整性误差。