Speaker: 徐怡冬（国家天文台）/ Yidong Xu (NAOC)

Venue: Gewu 4410

Time: 3:00 PM, Tuesday, 27th November, 2018

Abstract:

Cosmic dawn and the epoch of reionization (EoR) are among the most important but poorly understood epochs in the history of the universe. The process of hydrogen reionization can be described by the growth of ionized bubbles in the early stage, the percolation stage, and the shrinking of neutral islands during the late stage. While the growth of isolated ionized regions is well described by the “bubble model”, we would need the “island model” for the late epoch of reionization when the topology of the ionization field changes. It is found that the topological evolution of the ionization field can be unambiguously divided into five stages, and the Minkowski Functionals can be used as diagnostic tools to demarcate each evolutionary stage in topology. In particular, the Euler characteristic implicitly indicates the topological transition when one should use the “island model” instead of the “bubble model”. Among the various experiments designed for the cosmic dawn and the EoR signals, I’ll also introduce a lunar orbit low-frequency array that is being planned in China.

Personal Information:

徐怡冬，2011年于北京大学天文系获天体物理学博士学位，2008-2009年在意大利高等研究生院（SISSA）访问学习，2011-2014年在中科院国家天文台做博士后。2014年至今任职于中科院国家天文台，现为国家天文台宇宙暗物质和暗能量研究团组副研究员，硕士生导师。主要研究早期结构形成与宇宙大尺度结构，宇宙黎明与再电离，中性氢的射电观测。