Title: The Epoch of Reionization Show Chinese title

Title: 再电离纪元

Abstract: The Universe's dark ages end with the formation of the first generation of galaxies. These objects start emitting ultraviolet radiation that carves out ionized regions around them. After a sufficient number of ionizing sources have formed, the ionized fraction of the gas in the Universe rapidly increases until hydrogen becomes fully ionized. This period, during which the cosmic gas went from neutral to ionized, is known as the Universe's Epoch of Reionization . The Epoch of Reionization is related to many fundamental questions in cosmology, such as properties of the first galaxies, physics of (mini-)quasars, formation of very metal-poor stars and a slew of other important research topics in astrophysics. Hence uncovering it will have far reaching implications on the study of structure formation in the early Universe. This chapter reviews the current observational evidence for the occurrence of this epoch, its key theoretical aspects and main characteristics, and finally the various observational probes that promise to uncover it. A special emphasis is put on the redshifted 21 cm probe, the various experiments that are currently being either built or designed, and what we can learn from them about the Epoch of Reionization. Show Chinese abstract

Abstract: 宇宙的黑暗时代随着第一代星系的形成而结束。 这些天体开始发射紫外线辐射，在它们周围形成电离区域。 当足够多的电离源形成后，宇宙中气体的电离分数迅速增加，直到氢气完全电离。 这一期间，宇宙气体从中性转变为电离，被称为宇宙再电离时期。 再电离时期与宇宙学中的许多基础问题相关，例如早期星系的特性、（小型）类星体的物理性质、非常贫金属恒星的形成以及天体物理学中众多其他重要的研究课题。 因此，揭示这一时期将对早期宇宙结构形成的研究产生深远影响。 本章回顾了该时期的观测证据、关键理论方面和主要特征，以及最终可能揭示该时期的各种观测方法。 特别强调了红移21厘米探测法，目前正在进行建造或设计的各种实验，以及我们能从中了解关于再电离时期的什么信息。