标题： 红移星系中介入和关联的HI 21厘米吸收谱的对比研究 显示英文标题

标题： A comparative study of intervening and associated HI 21-cm absorption profiles in redshifted galaxies

摘要： 遥远宇宙中的恒星形成储库可以通过来自冷气体的HI 21厘米吸收来探测，这种冷气体要么与射电源相关联，要么来自视线方向上阻挡连续光源的星系内部。 为了测试吸积盘的性质是否可以从谱线形状预测，我们收集并分析了所有已知红移（z > 0.1）的HI 21厘米吸收谱线。 尽管单个光谱之间存在太多变化而无法定义典型的光谱轮廓，但我们确认关联吸收谱线平均而言比中介吸收谱线更宽。 普遍假设这是因为驱动中心引擎的高转速核区气体，在更为平静的中介吸收体中不存在这种气体。 通过建模平均关联和中介光谱的列密度分布，我们确认典型的关联吸收体中额外的低光学深度、宽分散分量来源于内核区内的气体。 关于在缺乏光学光谱的情况下预测吸积盘类型的潜力，我们已经将机器学习技术应用于55个关联光谱和43个中介光谱，每个测试模型在预测吸积盘类型时的准确率均超过80%。 鉴于下一代大型射电望远镜预计会发现大量21厘米信号，后续的光学光谱观测难以进行，这可能提供了一种强有力的新方法，用于确定吸收星系的性质。 显示英文摘要

摘要： The star-forming reservoir in the distant Universe can be detected through HI 21-cm absorption arising from either cool gas associated with a radio source or from within a galaxy intervening the sight-line to the continuum source. In order to test whether the nature of the absorber can be predicted from the profile shape, we have compiled and analysed all of the known redshifted (z > 0.1) HI 21-cm absorption profiles. Although between individual spectra there is too much variation to assign a typical spectral profile, we confirm that associated absorption profiles are on average, wider than their intervening counterparts. It is widely hypothesised that this is due to high velocity nuclear gas feeding the central engine, absent in the more quiescent intervening absorbers. Modelling the column density distribution of the mean associated and intervening spectra, we confirm that the additional low optical depth, wide dispersion component, typical of associated absorbers, arises from gas within the inner parsec. With regard to the potential of predicting the absorber type in the absence of optical spectroscopy, we have implemented machine learning techniques to the 55 associated and 43 intervening spectra, with each of the tested models giving a >80% accuracy in the prediction of the absorber type. Given the impracticability of follow-up optical spectroscopy of the large number of 21-cm detections expected from the next generation of large radio telescopes, this could provide a powerful new technique with which to determine the nature of the absorbing galaxy.