在再电离时期完成Ly-alpha发射者的普查
Completing the Census of Ly-alpha Emitters at the Reionization Epoch
摘要：
我们进行了扩展光谱确认的Ly-alpha发射器（LAEs）在z=6.5和5.7在斯巴鲁深场。现在，在z=6.5和5.7处，光谱确认的LAE总数分别为45和54，并且在z=6.5（5.7）处，至少81%（70%）的光度候选者已被光谱确定为真正的LAE。我们对Ly-alpha光度进行了仔细的测量，包括光度测量和光谱测量，以准确地确定Ly-alpha和rest-UV光度函数（LF）。在z=6.5处的Ly-alpha LF的大幅改进的评估显示至少在亮端处从z=5.7明显不足，并且即使在暗端也可能下降，尽管仍然存在小的不确定性。在z=6.5和5.7处的剩余UV LF具有良好的一致性，至少在亮端处，与Ly-alpha LF中观察到的差异形成鲜明对比。这些结果意味着星系际介质的中性分数从z=5.7增加到6.5。z=6.5时的静止帧等效宽度（EW_0）分布似乎系统地小于z=5.7时的EW_0分布，并且EW_0分布向较大的EW_0方向延伸。根据观测到的Ly-alpha LF和合理的EW_0-UV光度关系，可以再现静止-UV LF的亮端。整合这一休息紫外LF提供了第一次测量的贡献LAEs的光子预算所需的再电离。导出的紫外LF表明，部分LAEs的莱曼break星系之间的光子预算的贡献显着增加对微弱的幅度。低光度LAEs可能主导电离光子预算，虽然这种推断强烈依赖于不确定的Ly-alpha LF的暗端斜率。
英文摘要：
We carried out extended spectroscopic confirmations of Ly-alpha emitters (LAEs) at z=6.5 and 5.7 in the Subaru Deep Field. Now, the total number of spectroscopically confirmed LAEs is 45 and 54 at z=6.5 and 5.7, respectively, and at least 81% (70%) of our photometric candidates at z=6.5 (5.7) have been spectroscopically identified as real LAEs. We made careful measurements of the Ly-alpha luminosity, both photometrically and spectroscopically, to accurately determine the Ly-alpha and rest-UV luminosity functions (LFs). The substantially improved evaluation of the Ly-alpha LF at z=6.5 shows an apparent deficit from z=5.7 at least at the bright end, and a possible decline even at the faint end, though small uncertainties remain. The rest-UV LFs at z=6.5 and 5.7 are in good agreement, at least at the bright end, in clear contrast to the differences seen in the Ly-alpha LF. These results imply an increase in the neutral fraction of the intergalactic medium from z=5.7 to 6.5. The rest-frame equivalent width (EW_0) distribution at z=6.5 seems to be systematically smaller than z=5.7, and it shows an extended tail toward larger EW_0. The bright end of the rest-UV LF can be reproduced from the observed Ly-alpha LF and a reasonable EW_0-UV luminosity relation. Integrating this rest-UV LF provides the first measurement of the contribution of LAEs to the photon budget required for reionization. The derived UV LF suggests that the fractional contribution of LAEs to the photon budget among Lyman break galaxies significantly increases towards faint magnitudes. Low-luminosity LAEs could dominate the ionizing photon budget, though this inference depends strongly on the uncertain faint-end slope of the Ly-alpha LF.
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