现场测量HERA的原束：方法和初步结果
Measuring HERA's primary beam in-situ: methodology and first results
摘要：
21厘米宇宙学的核心挑战是将宇宙学信号从明亮的前景中分离出来。许多分离技术依赖于对天空和仪器响应（包括天线主波束）的准确了解。对于漂移扫描望远镜，例如不移动的氢时代再电离阵列\citep [HERA，][]{DeBoer 2017}，初级束表征特别具有挑战性，因为标准束校准例程不应用\citep{Cornwell2005}，并且当前技术需要望远镜分辨率下的精确源目录。我们提出了一个扩展的方法从\citet{Pober2012}，他们使用光束对称性，以创建一个网络的重叠源轨道，打破源通量密度和光束响应之间的简并，并允许他们同时估计。我们使用早期的HERA观测结果拟合了我们仪器的波束响应，发现我们的结果与电磁模拟吻合得很好，对于具有高信噪比的源，相对于峰值增益的功率下降到-20~dB水平。此外，我们还建立了一个包含90个源的源表，在151~MHz下通量密度为1.4~Jy。
英文摘要：
The central challenge in 21~cm cosmology is isolating the cosmological signal from bright foregrounds. Many separation techniques rely on the accurate knowledge of the sky and the instrumental response, including the antenna primary beam. For drift-scan telescopes such as the Hydrogen Epoch of Reionization Array \citep[HERA, ][]{DeBoer2017} that do not move, primary beam characterization is particularly challenging because standard beam-calibration routines do not apply \citep{Cornwell2005} and current techniques require accurate source catalogs at the telescope resolution. We present an extension of the method from \citet{Pober2012} where they use beam symmetries to create a network of overlapping source tracks that break the degeneracy between source flux density and beam response and allow their simultaneous estimation. We fit the beam response of our instrument using early HERA observations and find that our results agree well with electromagnetic simulations down to a -20~dB level in power relative to peak gain for sources with high signal-to-noise ratio. In addition, we construct a source catalog with 90 sources down to a flux density of 1.4~Jy at 151~MHz.
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