在再电离结束时高度不透明的大尺度星系空洞的证据
Evidence for a highly opaque large-scale galaxy void at the end of reionization
摘要：
我们提出的证据表明，在$z\sim5.7$的高有效LY $α$光学深度的区域与宇宙再电离的尾端的欠密区域。我们在$z=5.98$类星体J 0148 +0600的视场中使用Subaru Hyper Suprime-Cam进行了Lyman break Galerkin（LBG）的调查，其光谱在$5.5\le z\le 5.9$处呈现出异常长（$\sim160 \mathrm{cMpc}$）和不透明（$τ\gtrsim7$）的Ly $α$槽。LBG候选者被选择为位于红移范围内的低谷，并在类星体视线的90 cMpc范围内测量投影数密度。类星体位置的$8'$（或$\approx 19~\mathrm{cMpc}$）内的区域是整个场中密度最低的。空隙存在的意义估计为$99\%$。这与Becker等人报道的在$z=5.72$处Ly $α$发射体（LAEs）的显著不足是一致的，并表明LAEs的缺乏并不纯粹是由于高不透明度消除了Ly $α$发射，而是反映了在整个红移谷范围内星系的真实相干低密度。这些意见是一致的情况下，出现大的光学深度波动，由于在银河系占主导地位的紫外线背景的波动，或由于剩余的中性岛屿，预计从再电离完成的红移低至$z\lesssim5.5$。
英文摘要：
We present evidence that a region of high effective Ly$α$ optical depth at $z\sim5.7$ is associated with an underdense region at the tail end of cosmic reionization. We carried out a survey of Lyman-break Galaxies (LBGs) using Subaru Hyper Suprime-Cam in the field of the $z=5.98$ quasar J0148+0600, whose spectrum presents an unusually long ($\sim160 \mathrm{cMpc}$) and opaque ($τ\gtrsim7$) Ly$α$ trough at $5.5\le z\le 5.9$. LBG candidates were selected to lie within the redshift range of the trough, and the projected number densities were measured within 90~cMpc of the quasar sightline. The region within $8'$ (or $\approx 19~\mathrm{cMpc}$) of the quasar position is the most underdense of the whole field. The significance of the presence of the void is estimated to be $99\%$. This is consistent with the significant deficit of Ly$α$ emitters (LAEs) at $z=5.72$ reported by Becker et al. and suggests that the paucity of LAEs is not purely due to the removal of the Ly$α$ emission by the high opacity but reflects a real coherent underdensity of galaxies across the entire redshift range of the trough. These observations are consistent with scenarios in which large optical depth fluctuations arise due to fluctuations in the galaxy-dominant UV background or due to residual neutral islands that are expected from reionization that is completed at redshifts as low as $z\lesssim5.5$.
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