HERA模拟观察：寻找关闭HERA备忘录13
HERA Mock Observations: Looking for Closure HERA Memorandum Number 13
摘要：
本文研究了利用闭合相探测中性IGM在宇宙再电离过程中的HI 21 cm信号。闭合量具有独立于基于天线的校准项的独特优势。我们采用了Sims et al.（2016）的真实大面积天空模型。这些包括使用21厘米FAST产生的HI 21厘米信号的估计，加上弥漫的银河系同步辐射和河外点源的连续模型。我们采用CASA模拟器，并采用狄龙-帕森斯HERA配置，以产生一个紫外测量集。然后，我们使用AIPS计算作为频率函数的闭包阶段（“闭包谱”），并使用Python脚本进行后续分析。我们发现HI信号的闭合谱在频率上显示出戏剧性的结构，并且仅基于热噪声，冗余HERA-331阵列应该很容易检测到这些波动。相比之下，连续闭合谱中的频率结构比HI闭合谱中的频率结构平滑得多。不幸的是，当线信号和连续谱信号结合时，连续谱在10^3到10^4的电平上占主导地位，并且线信号丢失。我们研究了拟合和去除光滑的频率曲线的线加连续封闭谱，并发现连续本身显示足够的频率结构的封闭谱，以防止分离的连续和线基于这样的过程。我们还考虑了使用天空模型，在计算闭合光谱之前，从vitamos中减去连续谱。截断。
英文摘要：
We investigate the use of closure phase as a method to detect the HI 21cm signal from the neutral IGM during cosmic reionzation. Closure quantities have the unique advantage of being independent of antenna-based calibration terms. We employ realistic, large area sky models from Sims et al. (2016). These include an estimate of the HI 21cm signal generated using 21cm FAST, plus continuum models of both the diffuse Galactic synchrotron emission and the extragalactic point sources. We employ the CASA simulator and adopt the Dillon-Parsons HERA configuration to generate a uv measurement set. We then use AIPS to calculate the closure phases as a function of frequency ('closure spectra'), and python scripts for subsequent analysis. We find that the closure spectra for the HI signal show dramatic structure in frequency, and based on thermal noise alone, the redundant HERA-331 array should detect these fluctuations easily. Comparatively, the frequency structure in the continuum closure spectra is much smoother than that seen in the HI closure spectra. Unfortunately, when the line and continuum signals are combined, the continuum dominates the visibilities at the level of 10^3 to 10^4, and the line signal is lost. We have investigated fitting and removing smooth curves in frequency to the line plus continuum closure spectra, and find that the continuum itself shows enough structure in frequency in the closure spectra to preclude separation of the continuum and line based on such a process. We have also considered the subtraction of the continuum from the visibilities using a sky model, prior to calculation of the closure spectra. TRUNCATED.
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