论文标题
从HI排放中提取冷中性介质，深度学习：对高纬度的银河前景的影响
Extracting the cold neutral medium from HI emission with deep learning: Implications for Galactic foregrounds at high latitude
论文作者
论文摘要
解决中性氢（HI）的相结构对于理解星际培养基（ISM）的生命周期至关重要。但是，HI温度和密度的准确测量受到背景连续源的可用性的限制，用于测量HI吸收。在这里，我们测试了深度学习在没有光学深度信息的大面积上提取HI属性的使用。我们使用ISM的3D数值模拟的合成观测值训练1D卷积神经网络，以预测冷中性培养基（F_CNM）的比例，并校正光学深度（R_HI）的光学薄色HI柱密度（R_HI），从$ 21 \ rm \ rm \ rm \ rm \，单独使用CM $ $ $。我们将分析限制为高银河纬度（$ | b |> 30度），其中光谱线轮廓的复杂性被最小化。我们通过将结果与21 cm吸收的直接约束进行比较，我们验证网络是否准确地预测了F_CNM和R_HI。通过将网络应用于Galfa-Hi调查，我们生成了F_CNM和R_HI的大区域地图。尽管对冷中性培养基（CNM） - 富含较小的结构的总HI柱的总体贡献很小（约5％），但我们发现这些结构无处不在。我们的结果与与磁场排列的21 cm发射中观察到的小尺度结构的图像一致。最后，我们证明了HI色谱柱密度与灰尘变红（E（B-V））之间观察到的相关性随R_HI的增加而下降，这表明，即使在高纬度处，也应通过计算HI相结构来量化前景的银河系E（B-V）的未来努力，甚至在高纬度上量化前景E（B-V）也应提高忠诚度。
Resolving the phase structure of neutral hydrogen (HI) is crucial for understanding the life cycle of the interstellar medium (ISM). However, accurate measurements of HI temperature and density are limited by the availability of background continuum sources for measuring HI absorption. Here we test the use of deep learning for extracting HI properties over large areas without optical depth information. We train a 1D convolutional neural network using synthetic observations of 3D numerical simulations of the ISM to predict the fraction of cold neutral medium (f_CNM) and the correction to the optically-thin HI column density for optical depth (R_HI) from $21\rm\,cm$ emission alone. We restrict our analysis to high Galactic latitudes ($|b|>30 deg), where the complexity of spectral line profiles is minimized. We verify that the network accurately predicts f_CNM and R_HI by comparing the results with direct constraints from 21 cm absorption. By applying the network to the GALFA-HI survey, we generate large-area maps of f_CNM and R_HI. Although the overall contribution to the total HI column of cold neutral medium (CNM)-rich structures is small (~5%), we find that these structures are ubiquitous. Our results are consistent with the picture that small-scale structures observed in 21 cm emission aligned with the magnetic field are dominated by CNM. Finally, we demonstrate that the observed correlation between HI column density and dust reddening (E(B-V)) declines with increasing R_HI, indicating that future efforts to quantify foreground Galactic E(B-V) using HI, even at high latitudes, should increase fidelity by accounting for HI phase structure.
