z=6.4时，在QSO周围未检测到Lys $α$发射体：被QSO抑制？
No Ly$α$ emitters detected around a QSO at z=6.4: Suppressed by the QSO?
摘要：
了解类星体的紫外辐射如何影响星系形成对我们理解再电离时代至关重要。利用Subaru/Suprime-Cam上自制的窄带滤光片$NB906$，我们研究了z=6.4的类星体周围Ly $α$辐射源（LAE）的数密度。迄今为止，这是最高的红移窄带观测，其中LAEs周围的发光类星体的调查。由于Suprime-Cam的大视场，我们的测量区域为$\sim$ 5400~cMpc $^2$，远大于先前在z=5.7时的研究（$\sim$ 200 cMpc $^2$）。在这个领域，我们以前发现了一个7倍的密度过剩的莱曼break星系（LBG）。基于此，我们预期检测到$\sim$ 100 LAE，低至$NB906$ =25 ABmag。然而，我们的6.4小时曝光没有发现。得到的LAE数密度上限比空白字段低一个数量级以上。此外，这种较低密度的LAE跨越10 $p$ Mpc的大规模。一个简单的论点表明，来自类星体的强紫外辐射可以抑制$M_{vir}<10^{10}M_{\odot}$在距离类星体$p$ Mpc范围内的晕中的恒星形成，但场边缘的赤字（5 $p$ Mpc）仍有待解释。
英文摘要：
Understanding how QSO's UV radiation affects galaxy formation is vital to our understanding of reionization era. Using a custom made narrow-band filter, $NB906$, on Subaru/Suprime-Cam, we investigated the number density of Ly$α$ emitters (LAE) around a QSO at z=6.4. To date, this is the highest redshift narrow-band observation, where LAEs around a luminous QSO are investigated. Due to the large field-of-view of Suprime-Cam, our survey area is $\sim$5400~cMpc$^2$, much larger than previously studies at z=5.7 ($\sim$200 cMpc$^2$). In this field, we previously found a factor of 7 overdensity of Lyman break galaxies (LBGs). Based on this, we expected to detect $\sim$100 LAEs down to $NB906$=25 ABmag. However, our 6.4 hour exposure found none. The obtained upper limit on the number density of LAEs is more than an order lower than the blank fields. Furthermore, this lower density of LAEs spans a large scale of 10 $p$Mpc across. A simple argument suggests a strong UV radiation from the QSO can suppress star-formation in halos with $M_{vir}<10^{10}M_{\odot}$ within a $p$Mpc from the QSO, but the deficit at the edge of the field (5 $p$Mpc) remains to be explained.
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