从束卷积21 cm关联函数的多极统计恢复BAO标度
Statistical recovery of the BAO scale from multipoles of the beam-convolved 21cm correlation function
摘要：
尽管被设计为干涉仪，MeerKAT无线电阵列（SKA探路者）也可以用于自相关（“单碟”）模式，其中每个碟独立扫描天空。在这种模式下操作可以实现极高的测量速度，尽管角分辨率明显较低。本文研究了用这种低角分辨率的21厘米强度测绘测量的红移空间关联函数的多极来恢复重子声学振荡（BAO）标度。我们的方法是构建一个分析模型的多极的关联函数和他们的协方差矩阵，包括前景污染和光束分辨率的影响，然后我们用它来生成一个合奏的模拟数据向量，我们试图恢复的BAO规模。与以前的研究一致，我们发现，横向BAO尺度$α_{\perp}$的恢复受到阻碍的仪器光束的强平滑效应与增加红移，而径向尺度$α_\parallel$是更强大的。多极形式主义自然纳入横向信息时，它是可用的，但是，因此没有必要执行一个径向的分析。特别是，四极的关联函数保留了一个独特的BAO“颠簸”功能，即使是大的平滑尺度。我们还研究了BAO尺度恢复对波束模型准确性、前景去除切割的严重性以及协方差矩阵模型的准确性的鲁棒性，发现在所有情况下，径向BAO尺度可以以准确、无偏的方式恢复。
英文摘要：
Despite being designed as an interferometer, the MeerKAT radio array (an SKA pathfinder) can also be used in autocorrelation (`single-dish') mode, where each dish scans the sky independently. Operating in this mode allows extremely high survey speeds to be achieved, albeit at significantly lower angular resolution. We investigate the recovery of the baryon acoustic oscillation (BAO) scale from multipoles of the redshift-space correlation function as measured by a low angular resolution 21cm intensity mapping survey of this kind. Our approach is to construct an analytic model of the multipoles of the correlation function and their covariance matrix that includes foreground contamination and beam resolution effects, which we then use to generate an ensemble of mock data vectors from which we attempt to recover the BAO scale. In line with previous studies, we find that recovery of the transverse BAO scale $α_{\perp}$ is hampered by the strong smoothing effect of the instrumental beam with increasing redshift, while the radial scale $α_\parallel$ is much more robust. The multipole formalism naturally incorporates transverse information when it is available however, and so there is no need to perform a radial-only analysis. In particular, the quadrupole of the correlation function preserves a distinctive BAO `bump' feature even for large smoothing scales. We also investigate the robustness of BAO scale recovery to beam model accuracy, severity of the foreground removal cuts, and accuracy of the covariance matrix model, finding in all cases that the radial BAO scale can be recovered in an accurate, unbiased manner.
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