Observable Signatures of Reionization

根据最新的宇宙学理论，氢是大爆炸遗留下来的最丰富的元素，是在宇宙冷却到几千度以下时由自由电子和质子形成的。然而，最近的观测表明，在大爆炸后不到10亿年的时间里，这些宇宙氢的大部分被再次解离（即“再电离”）。人们普遍认为，宇宙中的氢是由宇宙中第一代恒星和黑洞发出的紫外线辐射再电离的。宇宙中第一个星系是如何以及何时形成的？它们对周围的宇宙气体有什么影响？这是当今观测和理论宇宙学中最令人兴奋的两个问题。该项目将结合分析计算和辐射传输问题的有限数值模拟来解决这些问题，并对未来尖端观测可能揭示的预期线索做出详细预测。特别是，它将识别观测探测器，这些探测器可以发出宇宙时间的信号，其中大部分氢被重新电离。氢再电离时代的理论和观测之间的相互作用将限制早期宇宙中第一个光源的性质以及基本的宇宙学参数（包括暗物质的性质）

AST 0204514LoebAccording to the most current theories of cosmology, hydrogen, the most abundant element left over from the big bang, was formed out of free electrons and protons when the Universe cooled below a temperature of a few thousand degrees. However, recent observations imply that most of this relic cosmic hydrogen was dissociated once again (i.e., `re-ionized') less than a billion years after the big bang. It is commonly believed that the cosmic hydrogen was re-ionized by the ultraviolet radiation emitted by the first generation of stars and black holes in the universe. How and when did the first galaxies form in the Universe? What was their effect on the surrounding cosmic gas? These are two of the most exciting questions in observational and theoretical cosmology today. This project will combine analytic calculations and limited numerical simulations of radiative transfer problems to address these questions and make detailed predictions for the expected clues that future, cutting-edge observations might reveal. In particular, it will identify observational probes that could signal the cosmic time at which most of the hydrogen was re-ionized. The interplay between theory and observations of the hydrogen re-ionization epoch will constrain the properties of the first sources of light in the early Universe as well as fundamental cosmological parameters (including the nature of the dark matter).***