论文标题
Lyman- $α$耦合和加热在宇宙黎明
Lyman-$α$ coupling and heating at Cosmic Dawn
论文作者
论文摘要
来自宇宙黎明的全局21-CM信号受各种加热和冷却过程的影响。我们使用基于所谓的“机翼近似”的Ly〜 $α$共振的谱围绕LY〜 $α$共振的分析表达来研究宇宙黎明的全球21厘米信号引起的加热对全球21厘米信号的加热影响。我们为散射校正得出了一种新的表达，并且首次为冷却而引起的简单近距离表达式，这是由于注入的ly〜 $α$光子而引起的。我们通过将ly〜 $α$背景强度通过四个数量级变化而进行简短的参数研究，并确定必须通过边缘协作复制强大的ly〜 $α$背景，尽管不够，以复制最近检测到的最近检测到的21 cm信号。我们表明，这种ly〜 $α$加热的大小比文献中先前通过两个数量级或更多的数量级要小。结果，即使是强大的〜$α$背景也与边缘测量相一致。我们还提供了有关文献中使用的LY〜 $α$加热率的不同表达式的详细讨论。
The global 21-cm signal from the cosmic dawn is affected by a variety of heating and cooling processes. We investigate the impact of heating due to Lyman-$α$ (Ly~$α$) photons on the global 21-cm signal at cosmic dawn using an analytical expression of the spectrum around the Ly~$α$ resonance based on the so-called `wing approximation'. We derive a new expression for the scattering correction and for the first time give a simple close-form expression for the cooling due to injected Ly~$α$ photons. We perform a short parameter study by varying the Ly~$α$ background intensity by four orders of magnitude and establish that a strong Ly~$α$ background is necessary, although not sufficient, in order to reproduce the recently detected stronger-than-expected 21-cm signal by the EDGES Collaboration. We show that the magnitude of this Ly~$α$ heating is smaller than previously estimated in the literature by two orders of magnitude or more. As a result, even a strong Ly~$α$ background is consistent with the EDGES measurement. We also provide a detailed discussion on different expressions of the Ly~$α$ heating rate used in the literature.
