标题： 再电离时期的中性氧演化及其在估算中性氢分数中的应用 显示英文标题

标题： Evolution of Neutral Oxygen During the Epoch of Reionization and its Use in Estimating the Neutral Hydrogen Fraction

摘要： 我们利用通过Technicolor Dawn模拟快照绘制的合成视线，探讨了中性氧（OI）吸收体的统计特性如何响应氢再电离。 星系周围介质（CGM）的电离状态最初大致跟踪星系间介质（IGM），但自$z=8$起，由于自我屏蔽效应，CGM变得系统性更中性。 弱吸收体追踪远离星系晕的弥散气体，因此它们首先被电离；而较强的系统对再电离的敏感度较低。 由于持续的富集和电离前沿逐渐侵入越来越过密的气体之间的竞争，总体OI覆盖分数随时间缓慢下降。 尽管新星系的持续形成部分抵消了这一趋势，但弥散气体的电离导致预测的OI吸收体视线出现率在重叠时期急剧下降，这在定性上与观测结果一致。 与最近观测到的$z\approx6$的等效宽度（EW）分布相比，这些模拟低估了具有$EW \geq 0.1 \unicode{x212B}$特征的系统，但成功再现了较弱的系统$EW \geq 0.05 \unicode{x212B}$。 到$z\approx5$时，$EW < 0.1 \unicode{x212B}$系统的发生率被高估，这与之前表明的模拟电离背景在$z<6$处太弱的结论一致。 SiII和SiIV的总列密度追踪总的氧列密度，因此OI和SiII+SiIV共动质量密度之比追踪再电离的进展。 这种探针在$x_{HI} > 10\%$所在的区域可能尤其有用。 显示英文摘要

摘要： We use synthetic sightlines drawn through snapshots of the Technicolor Dawn simulations to explore how the statistics of neutral oxygen OI absorbers respond to hydrogen reionization. The ionization state of the circumgalactic medium (CGM) initially roughly tracks that of the intergalactic medium, but beginning at $z=8$ the CGM grows systematically more neutral owing to self-shielding. Weak absorbers trace diffuse gas that lies farther from halos, hence they are ionized first, whereas stronger systems are less sensitive to reionization. The overall OI covering fraction decreases slowly with time owing to competition between ongoing enrichment and gradual encroachment of ionization fronts into increasingly overdense gas. While the declining covering fraction is partially offset by continued formation of new halos, the ionization of the diffuse gas causes the predicted line-of-sight incidence rate of OI absorbers to decline abruptly at the overlap epoch, in qualitative agreement with observations. In comparison to the recently-observed equivalent width (EW) distribution at $z\approx6$, the simulations underproduce systems with $EW \geq 0.1 \unicode{x212B}$, although they reproduce weaker systems with $EW \geq 0.05 \unicode{x212B}$. By $z\approx5$, the incidence of $EW < 0.1 \unicode{x212B}$ systems are overproduced, consistent with previous indications that the simulated ionizing background is too weak at $z<6$. The summed column densities of SiII and SiIV trace the total oxygen column, and hence the ratio of the OI and SiII + SiIV comoving mass densities traces the progress of reionization. This probe may prove particularly useful in the regime where $x_{HI} > 10\%$