THE HYDROGEN EPOCH OF REIONIZATION ARRAY DISH. II. CHARACTERIZATION OF SPECTRAL STRUCTURE WITH ELECTROMAGNETIC SIMULATIONS AND ITS SCIENCE IMPLICATIONS
THE HYDROGEN EPOCH OF REIONIZATION ARRAY DISH. II. CHARACTERIZATION OF SPECTRAL STRUCTURE WITH ELECTROMAGNETIC SIMULATIONS AND ITS SCIENCE IMPLICATIONS
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DOI：
10.3847/0004-637x/831/2/196
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发表时间：
2016-02
期刊：
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通讯作者：
A. Ewall-Wice;R. Bradley;R. Bradley;D. DeBoer;J. Hewitt;A. Parsons;J. Aguirre;Z. Ali;J. Bowman;Carina Cheng;A. Neben;Nipanjana Patra;N. Thyagarajan;M. Venter;E. D. L. Acedo;J. Dillon;R. Dickenson;P. Doolittle;D. Egan;Mike Hedrick;P. Klima;S. Kohn;Patrick Schaffner;J. Shelton;B. Saliwanchik;H. Taylor;R. Taylor;M. Tegmark;B. Wirt
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作者：
A. Ewall-Wice;R. Bradley;R. Bradley;D. DeBoer;J. Hewitt;A. Parsons;J. Aguirre;Z. Ali;J. Bowman;Carina Cheng;A. Neben;Nipanjana Patra;N. Thyagarajan;M. Venter;E. D. L. Acedo;J. Dillon;R. Dickenson;P. Doolittle;D. Egan;Mike Hedrick;P. Klima;S. Kohn;Patrick Schaffner;J. Shelton;B. Saliwanchik;H. Taylor;R. Taylor;M. Tegmark;B. Wirt
我们使用时域电磁模拟来确定氢时代再电离阵列（HERA）天线的频谱特性。这些模拟是一个多方面的运动的一部分，以确定盘的设计的有效性，以获得从再电离时代的红移21厘米发射的检测。我们的模拟表明，HERA的悬挂式馈电和抛物面反射器之间存在反射，在150 ns时低于−40 dB，对于合理的阻抗匹配，对HERA限制EoR参数的能力影响可以忽略不计。因此，尽管它们引入了反射，但盘对于以相对较低的成本增加EoR实验的灵敏度是有效的。我们发现，HERA馈源的圆柱形裙部中的电磁谐振（旨在减少交叉耦合和光束椭圆度）在大延迟（200 ns时为-40 dB）时引入了显著的功率，这可能导致可测量的傅立叶模式的一些损失和灵敏度的适度降低。即使在这种结构的存在下，我们发现，天线的频谱响应是足够平滑的延迟滤波，以包含前景发射在视线波数低于k 0.2 h Mpc−1，在该地区，目前的纸张实验操作。将这些结果转化为Fisher矩阵分析，我们发现在我们的模拟中观察到的光谱结构对HERA可以实现的与再电离天体物理学相关的参数的严格约束只有很小的影响。
We use time-domain electromagnetic simulations to determine the spectral characteristics of the Hydrogen Epoch of Reionization Arrays (HERA) antenna. These simulations are part of a multi-faceted campaign to determine the effectiveness of the dish’s design for obtaining a detection of redshifted 21 cm emission from the epoch of reionization. Our simulations show the existence of reflections between HERA’s suspended feed and its parabolic dish reflector that fall below −40 dB at 150 ns and, for reasonable impedance matches, have a negligible impact on HERA’s ability to constrain EoR parameters. It follows that despite the reflections they introduce, dishes are effective for increasing the sensitivity of EoR experiments at a relatively low cost. We find that electromagnetic resonances in the HERA feed’s cylindrical skirt, which is intended to reduce cross coupling and beam ellipticity, introduces significant power at large delays (−40 dB at 200 ns), which can lead to some loss of measurable Fourier modes and a modest reduction in sensitivity. Even in the presence of this structure, we find that the spectral response of the antenna is sufficiently smooth for delay filtering to contain foreground emission at line-of-sight wave numbers below k∥ ≲ 0.2 h Mpc−1, in the region where the current PAPER experiment operates. Incorporating these results into a Fisher Matrix analysis, we find that the spectral structure observed in our simulations has only a small effect on the tight constraints HERA can achieve on parameters associated with the astrophysics of reionization.