标题： 使用人工神经网络从EDGES数据中提取21厘米全局信号 显示英文标题

标题： Using Artificial Neural Networks to extract the 21-cm Global Signal from the EDGES data

摘要： 中性氢的红移21厘米信号是我们宇宙从形成第一颗恒星（宇宙黎明）到整个宇宙从完全中性转变为完全电离（再电离）时期的演化过程的一个有前景的探测工具。这一中性氢谱线最显著的特征在于它可以在整个频率范围内作为一个天空平均的连续信号被观测到，或者可以通过干涉仪测量其波动。 然而，21厘米信号非常微弱，并且被更亮的银河和星系际前景所主导，这使得观测成为一个挑战。我们使用了不同的物理模型来模拟21厘米全天空信号的各种实现，包括添加一个过量射电背景以匹配EDGES 21厘米信号的幅度。首先，我们使用人工神经网络(ANN)从这些模拟数据集中提取天体物理参数。然后，通过添加一个基于物理的前景模型生成模拟观测，同样使用人工神经网络从这些数据中提取天体物理参数。我们的预测从模拟观测得到的 $R^2$ 得分在0.65至0.89之间。我们使用这个ANN来预测EDGES数据作为输入时的信号参数。我们发现重建的信号紧密地模仿了报告检测的幅度。恢复的参数可以用来推断高红移下气体的物理状态。 显示英文摘要

摘要： The redshifted 21-cm signal of neutral Hydrogen is a promising probe into the period of evolution of our Universe when the first stars were formed (Cosmic Dawn), to the period where the entire Universe changed its state from being completely neutral to completely ionized (Reionization). The most striking feature of this line of neutral Hydrogen is that it can be observed across an entire frequency range as a sky-averaged continuous signature, or its fluctuations can be measured using an interferometer. However, the 21-cm signal is very faint and is dominated by a much brighter Galactic and extra-galactic foregrounds, making it an observational challenge. We have used different physical models to simulate various realizations of the 21-cm Global signals, including an excess radio background to match the amplitude of the EDGES 21-cm signal. First, we have used an artificial neural network (ANN) to extract the astrophysical parameters from these simulated datasets. Then, mock observations were generated by adding a physically motivated foreground model and an ANN was used to extract the astrophysical parameters from such data. The $R^2$ score of our predictions from the mock-observations is in the range of 0.65-0.89. We have used this ANN to predict the signal parameters giving the EDGES data as the input. We find that the reconstructed signal closely mimics the amplitude of the reported detection. The recovered parameters can be used to infer the physical state of the gas at high redshifts.