标题： SKA时代中的星系间介质和宇宙网观测 显示英文标题

标题： Observations of the Intergalactic Medium and the Cosmic Web in the SKA era

摘要： 星系与其环境（即星系际介质，IGM）之间的相互作用是星系形成的一个重要方面。在星系演化中最基本但尚未回答的问题之一是气体如何在星系内外循环，以及它是如何进入星系以支持恒星形成。我们有多种证据表明，观测到的恒星形成演化需要在所有宇宙尺度上持续从IGM吸积气体。这种气体大部分仍未被发现，而未解决的问题是这些气体位于何处以及吸积的物理机制是什么。 预计这些气体嵌入在一个由片状和纤维状结构组成的扩展宇宙网中。这样的大尺度气体纤维被宇宙学数值模拟预测，近年来这些模拟取得了显著进展。这些模拟不仅模拟了宇宙网的大尺度结构，还研究了中性气体成分。 为了真正深入了解IGM中中性氢的分布，必须使用亚角分分辨率，在天空上的大面积范围内探测NHI=10^18 cm^-2及以下的列密度。这些是今天已知的附近星系周围最微弱结构的密度，尽管大多通过单天线望远镜发现，这些望远镜没有足够的分辨率来解析这些结构并研究其动力学特性。 现有的干涉仪缺乏收集功率或短基线，无法达到通常低于NHI=10^19 cm^-2的亮度灵敏度。使用现有设备达到更低的列密度是可行的，但需要极长的观测时间。SKA（平方公里阵列）将首次突破这些限制，使干涉观测比当前干涉仪深一个数量级，并且比单天线望远镜的线性分辨率提高一个数量级。 显示英文摘要

摘要： The interaction of galaxies with their environment, the Intergalactic Medium (IGM), is an important aspect of galaxy formation. One of the most fundamental, but unanswered questions in the evolution of galaxies is how gas circulates in and around galaxies and how it enters the galaxies to support star formation. We have several lines of evidence that the observed evolution of star formation requires gas accretion from the IGM at all times and on all cosmic scales. This gas remains largely unaccounted for and the outstanding questions are where this gas resides and what the physical mechanisms of accretion are. The gas is expected to be embedded in an extended cosmic web made of sheets and filaments. Such large-scale filaments of gas are expected by cosmological numerical simulations, which have made significant progress in recent years. Such simulations do not only model the large scale structure of the cosmic web, but also investigate the neutral gas component. To truly make significant progress in understanding the distribution of neutral hydrogen in the IGM, column densities of NHI=10^18 cm-2 and below have to be probed over large areas on the sky at sub-arcminute resolution. These are the densities of the faintest structures known today around nearby galaxies, though mostly found with single dish telescopes which do not have the resolution to resolve these structures and investigate any kinematics. Existing interferometers lack the collecting power or short baselines to achieve brightness sensitivities typically below NHI=10^19 cm-2. Reaching lower column densities with current facilities is feasible, however requires prohibitively long observing times. The SKA will for the first time break these barriers, enabling interferometric observations an order of magnitude deeper than current interferometers and with an order of magnitude better linear resolution than single-dish telescopes.