论文标题
Superborg：$ z \ sim8 $在HST平行字段中对点源的探索
SuperBoRG: Exploration of point sources at $z\sim8$ in HST parallel fields
论文作者
论文摘要
为了将QUASAR的搜索量扩展到亮度功能的尖端，我们探索了Superborg的Redshift $ Z \ sim8 $的点源候选者，$ \ sim $ 0.4度$^2 $ Archival Mediad-Deep（$ M _ {$ m _ {\ rm f160w} $ sim 26.5 $ abble ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir ir imag太空望远镜（HST）。使用Lyman-Break Technique选择初始候选人。然后，我们仔细分析源形态，并以$ z \ sim8 $的形式稳健地识别3点源。光度红移分析表明，它们优先符合半乳酸模板，我们得出的结论是，它们不太可能是包括棕色矮人在内的低$ z $ interlopers。在其中一个点源之一中可以看到明显的IRAC CH2通量过量，如果源具有强大的H $β$+[O III]发射，其静止框架等效宽度为$ \ sim3000 $ aa。但是，使用Keck/Mosfire进行的深度光谱数据并未揭示物体中的$α$排放。结合估计的H $β$+[O III]等效宽度，我们对其Ly $α$逃逸分数$ f _ {\ rm esc，lyα} <2 \％$置于上限。我们估计这些点源的数量密度$ \ sim1 \ times10^{ - 6} $ mpc $^{ - 3} $ mag $ $^{ - 1} $ at $ m _ {\ rm uv} \ sim-23 $。对我们结果的最终解释仍然没有定论：从$ $ $ $ quasars的低$ z $研究中推断出来，可能需要$> 100 \ times $ usevery量才能找到一种亮度之一。詹姆斯·韦伯（James Webb）太空望远镜将能够最终确定我们发光点源候选者的性质，而罗马太空望远镜将探测$ \ sim 200 $乘以天空区域，并在此HST研究中考虑了相同的观察时间。
To extend the search for quasars in the epoch of reionization beyond the tip of the luminosity function, we explore point source candidates at redshift $z\sim8$ in SuperBoRG, a compilation of $\sim$0.4deg$^2$ archival medium-deep ($m_{\rm F160W}\sim 26.5$ABmag, 5$σ$) parallel IR images taken with the Hubble Space Telescope (HST). Initial candidates are selected by using the Lyman-break technique. We then carefully analyze source morphology, and robustly identify 3 point sources at $z\sim8$. Photometric redshift analysis reveals that they are preferentially fit by extra-galactic templates, and we conclude that they are unlikely to be low-$z$ interlopers, including brown dwarfs. A clear IRAC ch2 flux excess is seen in one of the point sources, which is expected if the source has strong H$β$+[O III] emission with rest-frame equivalent width of $\sim3000$AA. Deep spectroscopic data taken with Keck/MOSFIRE, however, do not reveal Ly$α$ emission from the object. In combination with the estimated H$β$+[O III] equivalent width, we place an upper limit on its Ly$α$ escape fraction $f_{\rm esc, Lyα}< 2 \%$. We estimate the number density of these point sources $\sim1\times10^{-6}$Mpc$^{-3}$mag$^{-1}$ at $M_{\rm UV}\sim-23$mag. The final interpretation of our results remains inconclusive: extrapolation from low-$z$ studies of $faint$ quasars suggests that $>100\times$ survey volume may be required to find one of this luminosity. The James Webb Space Telescope will be able to conclusively determine the nature of our luminous point source candidates, while the Roman Space Telescope will probe $\sim 200$ times the area of the sky with the same observing time considered in this HST study.
