AI 中文总结
研究利用电磁模拟偶极天线量化黑暗时代21厘米功率谱中的前景污染问题。通过模拟可见度测量值，考虑天线波束、天空模型等，研究月球风化层变化影响，发现风化层特性影响前景功率抑制，强调准确建模前景和风化层的重要性。
AI 中文摘要
宇宙黑暗时代的高红移21厘米信号为宇宙学带来了令人兴奋的前沿领域，有望在没有复杂天体物理现象的情况下观测宇宙密度场的大量傅里叶模式。由于地球电离层和人为干扰影响这些低频，月球背面被认为是进行此类实验的理想地点。这些频率下的明亮同步辐射前景预计在频谱上是平滑的，从而占据频谱傅里叶模式的一个子集，为黑暗时代信号留下一个可观测的“窗口”。然而，实际上，由于仪器伪像，前景中会出现频谱结构，导致前景功率溢出到可观测窗口。在本文中，我们针对给定的一些天线波束、天空模型和基线配置，对一组模拟的可见度测量值量化了这种溢出。值得注意的是，我们使用两个数值模拟波束模型，研究了月球风化层变化对前景溢出的影响，这两个模型在下面有1层和4层基底材料。我们发现，风化层材料特性会在波束中引起不需要的频谱结构，这可能会阻碍所需水平的前景功率抑制。详细的频谱行为取决于所使用的月球风化层模型，因此为黑暗时代宇宙学生成准确的前景模型和月球风化层模型至关重要。
英文摘要
The highly-redshifted 21 cm signal from the cosmic Dark Ages presents an exciting frontier for cosmology, with the potential to observe a large number of Fourier modes of the cosmic density field in the absence of complicating astrophysical phenomena. Because the Earth's ionosphere and human-generated interference affect these low radio frequencies, the lunar far side - the most radio-quiet region in the inner solar system - is considered the ideal site to conduct such an experiment. The bright synchrotron foregrounds at these frequencies are expected to be spectrally smooth and thus occupy a subset of spectral Fourier modes, leaving an observable "window" to the Dark Ages signal. However, in practice, spectral structure arises in foregrounds due to instrumental artifacts, leading to a spillover of foreground power into the observable window. In this paper, we quantify this spillover for a set of simulated visibility measurements given a number of antenna beams, sky models, and baseline configurations. Notably, we examine the effects on foreground spillover due to variations in the lunar regoliths using two numerically simulated beam models with 1 and 4 layers of substrate materials underneath. We find that the regolith material properties can induce unwanted spectral structure in the beams, which potentially prevents foreground power suppression at the levels required. The detailed spectral behavior depends on the lunar regolith model used, making it paramount to produce both accurate models of foregrounds and of the lunar regolith for Dark Ages cosmology.
Comments14 pages, 9 figures
