Reconstructing The Cosmic Density Field to Understand the Local Intergalactic Medium and its Relation to Galaxies

莫博士和他的团队将利用斯隆数字巡天（SDSS），一项对附近星系的大型巡天，重建当前本地宇宙中暗物质的分布。在大型引力n体模拟的帮助下，他们将推断出在宇宙历史的早期，在星系开始形成恒星之前，物质的分布一定是怎样的。在早期，以气体形式存在的正常物质会与暗物质均匀混合。然后，该团队将使用光滑粒子流体动力学模拟来跟踪暗物质和气体的综合发展，在各种假设下，气体如何变成恒星，以及这些恒星如何将能量反馈给星系间气体。他们的目标包括测试一个目前流行的模型，根据该模型，气体在落入大质量系统时受到冲击和加热，但悄悄地流入较小的星系，保持低温，以便容易形成恒星。他们将估计有多少气体与各种宇宙环境有关，比如星系的细丝和薄片，并研究恒星内部核反应产生的金属是如何进入星系间气体的。一名研究生将通过参与研究得到培训，该团队还希望为本科生提供小规模的研究项目。来自SDSS星表的密度场，以及来自模拟的各种星表，将提供给天文学界。该团队将绘制暗物质、发光星系和星系间气体的三维重建分布图，用于教学和公众宣传。

Dr. Mo and his team will use the Sloan Digital Sky Survey (SDSS), a large survey of nearby galaxies, to reconstruct the distribution of dark matter in the local Universe at the present time. With the aid of large gravitational N-body simulations, they will deduce what that matter distribution must have been earlier in cosmic history, before the galaxies began to form their stars. At those early times, normal matter in the form of gas would have been evenly mixed with the dark matter. The team will then use smooth-particle hydrodynamic simulations to follow the combined development of the dark matter and the gas, under various assumptions about how the gas is turned into stars, and how those stars feed energy back into the intergalactic gas. Their aims include testing a currently-popular model, according to which gas is shocked and heated as it falls into massive systems, but flows quietly into smaller galaxies, remaining cold so that it can readily form stars. They will estimate how much gas is associated with various cosmic environments, such as filaments and sheets of galaxies, and examine how metals produced by the nuclear reactions inside stars are fed into the intergalactic gas.A graduate student will be trained by participating in the research, and the team also expects to offer small-scale research projects for undergraduates. The density fields derived from the SDSS catalog, and various catalogs from the simulations, will be made available to the astronomical community. The team will produce three-dimensional maps of the reconstructed distribution of dark matter, luminous galaxies and intergalactic gas, for use in teaching and public outreach.