类星体冒充者：两颗由大质量恒星驱动的再电离时期极紫外明亮星系（$M_{\rm UV}\u2248-23.5$）
Quasar Impostors: Two Extremely UV-Bright ($M_{\rm UV}\approx-23.5$) Reionisation-Epoch Galaxies Powered by Very Massive Stars
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中文总结 AI 辅助
本研究发现两颗曾被归为类星体的再电离时期极亮星系，证实大质量恒星可驱动这类星系，需重新审视重叠区域的源分类及相关统计特征。
中文摘要 AI 辅助
再电离时期星系紫外光度函数的极亮端仍缺乏精确约束，尤其在星系与类星体光度函数重叠、源分类变得模糊的区域。我们呈现了JWST/NIRSpec与ALMA 6波段对J1450-0144（$z=6.627$）和J1429-0104（$z=6.796$）的观测结果，这两个$M_{\rm UV}\u2248-23.5$的源最初被SHELLQs归类为暗弱类星体。NIRSpec观测显示它们具有蓝色紫外连续谱、N V、Si IV和C IV的强P Cygni轮廓、宽He II $\u03bb1640$发射线（静止帧等效宽度分别为$8.8\u00b11.2$和$3.7\u00b11.1$ Å）以及窄星云线，因此将两者重新归类为极紫外发光星系。标准星族合成模型无法同时重现强He II和星风特征，而纳入大质量恒星（VMS；$M\u2273100\\,M_\odot$）及专用星风模型的模型可以做到。这些模型给出J1450-0144的恒星形成持续时间为2-4 Myr，J1429-0104的允许范围更宽，恒星质量为$\u039b(M_\star/M_\odot)\u22489.2$-$9.9$，恒星形成率约为$300$-$540\\,M_\odot\\,{\rm yr}^{-1}$。在相同的VMS星风模型下，等效宽度诊断表明J1429-0104的上限质量$M_{\rm up}\u2273225\\,M_\odot$，而J1450-0104甚至超出了$M_{\rm up}=475\\,M_\odot$的网格范围。ALMA在两个系统中都探测到明亮的[C II] 158 $\u03bcm$发射，$L_{\rm [CII]}$分别约为$0.8$和$4.1\u00d710^{9}\\,L_\odot$。J1429-0104还显示出明亮的尘埃连续谱，且[C II]和尘埃都与其紫外发射偏移了约$5.4$ kpc。这些源表明，大质量恒星可以驱动宇宙黎明时期一些最紫外明亮的星系，且在重叠区域的源分类以及由此推断的星系和类星体统计特征需要重新审视。
英文摘要
The extreme bright end of the galaxy UV luminosity function during reionisation remains poorly constrained, particularly where the galaxy and quasar luminosity functions overlap and source classification becomes ambiguous. We present JWST/NIRSpec and ALMA Band-6 observations of J1450-0144 ($z=6.627$) and J1429-0104 ($z=6.796$), two $M_{\rm UV}\simeq-23.5$ sources originally classified as faint quasars by SHELLQs. NIRSpec reveals blue UV continua, strong P Cygni profiles in N V, Si IV, and C IV, broad He II $\lambda1640$ emission with rest-frame equivalent widths of $8.8\pm1.2$ and $3.7\pm1.1$ Å, respectively, and narrow nebular lines, reclassifying both as extremely UV-luminous galaxies. Standard population-synthesis models cannot simultaneously reproduce the strong He II and wind features, whereas models incorporating very massive stars (VMS; $M\gtrsim100\,M_\odot$) with dedicated wind prescriptions can. These models favor a star-formation duration of 2-4 Myr for J1450-0144, with a broader allowed range for J1429-0104, stellar masses of $\log(M_\star/M_\odot)\approx9.2$-$9.9$, and star-formation rates of $\simeq300$-$540\,M_\odot\,{\rm yr}^{-1}$. Under the same VMS wind models, equivalent-width diagnostics imply $M_{\rm up}\gtrsim225\,M_\odot$ for J1429-0104, while J1450-0144 lies beyond even the $M_{\rm up}=475\,M_\odot$ grid. ALMA detects luminous [C II] 158 $μ$m emission in both systems, with $L_{\rm [CII]}\approx0.8$ and $4.1\times10^{9}\,L_\odot$, respectively. J1429-0104 additionally shows bright dust continuum, with both [C II] and dust offset by $\sim5.4$ kpc from its UV emission. These sources demonstrate that VMS can power some of the most UV-luminous galaxies at cosmic dawn and show that source classifications, and hence the inferred demographics of both galaxies and quasars in the crossover regime, need revisiting.
