标题： 再电离时期最明亮的Lyman-$α$发射体中存在类似第三星族恒星种群的证据：光谱确认 显示英文标题

标题： Evidence for PopIII-like stellar populations in the most luminous Lyman-$α$ emitters at the epoch of re-ionisation: spectroscopic confirmation

摘要： 微弱的莱曼-$\alpha$ (Ly$\alpha$) 发射体在再电离时期（z~6-7）变得越来越稀少。 然而，来自一个非常大的 (~5deg$^2$) Ly$\alpha$ 在 z=6.6 的调查（Matthee 等人。 2015）显示，对于最明亮的发射体来说情况并非如此。 在这里，我们介绍了 COSMOS 区域中两个最明亮的 z~6.6 Ly$\alpha$候选体的后续观测：`MASOSA' 和 `CR7'。 我们使用 X-SHOOTER、SINFONI 和 FORS2（VLT），以及 DEIMOS（Keck），以毫无疑问地确认这两个候选体。 我们发现 MASOSA 和 CR7 的红移分别为 z=6.541 和 z=6.604。 MASOSA在Ly$\alpha$处有强检测，线宽为$386\pm30$km/s（FWHM），且具有高的EW$_0$（>200\AA ），但在连续谱中未被检测到。 CR7的观测Ly$\alpha$光度为$10^{43.93\pm0.05}$erg/s，是目前在z>6处发现的最明亮的Ly$\alpha$发射体。 CR7显示出一条狭窄的Ly$\alpha$线，FWHM为$266\pm15$km/s，在近红外（静止框架紫外线，$\beta=-2.3\pm0.1$）中被检测到，在$J$中有超额，并且在IRAC/斯皮策望远镜中也被强烈检测到。 我们检测到一条窄的HeII1640$\AA$发射线 ($6\sigma$)，这解释了在$J$带测光中观察到的过量 (EW$_0$~80\AA )。 我们在X-SHOOTER光谱中从紫外到近红外没有发现其他发射线 (HeII/OIII]1663A>3 和 HeII/CIII]1908A>2.5)。 我们发现CR7最好由一个类似PopIII的星群来解释，该星群主导了红移后的紫外和电离气体发射，以及一个更正常的星群，该星群主导了质量。 HST/WFC3观测显示，光确实分为一个非常蓝的组分，与Ly$\alpha$和HeII发射一致，以及两个红色组分（约5 kpc远离），这些组分主导了质量。 我们的发现与PopIII波的理论预测一致， PopIII恒星形成从最初的恒星形成区域迁移出去。 显示英文摘要

摘要： Faint Lyman-$\alpha$ (Ly$\alpha$) emitters become increasingly rarer towards the re-ionisation epoch (z~6-7). However, observations from a very large (~5deg$^2$) Ly$\alpha$ survey at z=6.6 (Matthee et al. 2015) show that this is not the case for the most luminous emitters. Here we present follow-up observations of the two most luminous z~6.6 Ly$\alpha$ candidates in the COSMOS field: `MASOSA' and `CR7'. We used X-SHOOTER, SINFONI and FORS2 (VLT), and DEIMOS (Keck), to confirm both candidates beyond any doubt. We find redshifts of z=6.541 and z=6.604 for MASOSA and CR7, respectively. MASOSA has a strong detection in Ly$\alpha$ with a line width of $386\pm30$ km/s (FWHM) and with high EW$_0$ (>200 \AA), but it is undetected in the continuum. CR7, with an observed Ly$\alpha$ luminosity of $10^{43.93\pm0.05}$erg/s is the most luminous Ly$\alpha$ emitter ever found at z>6. CR7 reveals a narrow Ly$\alpha$ line with $266\pm15$ km/s FWHM, being detected in the NIR (rest-frame UV, with $\beta=-2.3\pm0.1$) with an excess in $J$, and also strongly detected in IRAC/Spitzer. We detect a narrow HeII1640$\AA$ emission line ($6\sigma$) which explains the excess seen in the $J$ band photometry (EW$_0$~80 \AA). We find no other emission lines from the UV to the NIR in our X-SHOOTER spectra (HeII/OIII]1663A>3 and HeII/CIII]1908A>2.5). We find that CR7 is best explained by a combination of a PopIII-like population which dominates the rest-frame UV and the nebular emission, and a more normal stellar population which dominates the mass. HST/WFC3 observations show that the light is indeed spatially separated between a very blue component, coincident with Ly$\alpha$ and HeII emission, and two red components (~5 kpc away), which dominate the mass. Our findings are consistent with theoretical predictions of a PopIII wave, with PopIII star formation migrating away from the original sites of star formation.