标题： RIOJA JWST 和 ALMA 揭示了在$z=6.81$的恒星形成星系中不均匀且复杂的星际介质结构 显示英文标题

标题： RIOJA. JWST and ALMA unveil the inhomogeneous and complex ISM structure in a star-forming galaxy at $z=6.81$

摘要： 我们报告在星形成星系COS-2987中发现了一个复杂、两相的电离气体结构，其红移为$z = 6.81$，这是由JWST/NIRSpec IFS和ALMA观测前所未有的协同作用揭示的。 这些观测检测到了关键的发射线，包括[OII]$\lambda\lambda$ 3727, 3730, [OIII] 4364, [OIII] $\lambda\lambda$ 4960, 5008, [OIII] 88 $\mu$m，以及H$\alpha$和H$\beta$。 仅JWST光谱学表明星际介质（ISM）的特性对于红移为$z\sim7$的星系来说是典型的。 这些包括低尘埃消光（$A_{\rm V} \approx 0.14$mag）、中等电子密度（$n_{\rm e} \approx 500$cm$^{-3}$）和低气相金属丰度（$\sim10\%$）。然而，ALMA检测到的强远红外[OIII] 88$\mu$m发射无法用具有均匀电子密度和温度的单相电离介质来解释。 相反，一个两阶段的ISM模型，包括紧凑、高温、高密度气体成分（$T_e \approx 26,000$K；$n_e \approx 600 \mathrm{cm}^{-3}$）和扩展、较冷、低密度成分（$T_e \approx 8,000$K；$n_e \approx 50 \mathrm{cm}^{-3}$），成功地再现了观测到的[OIII] 88$\mu$m/[OIII] 5008 Å和[OIII] 4364 Å/[OIII] 5008 Å的线比率，两个阶段之间的体积比为1：300。我们的结果表明，JWST仅探测了ISM的一部分，并突显了结合JWST和ALMA以揭示早期星系密度分层ISM的关键重要性。 显示英文摘要

摘要： We report the discovery of a complex, two-phase ionized gas structure in the star-forming galaxy COS-2987 at $z = 6.81$, revealed by the unprecedented synergy between JWST/NIRSpec IFS and ALMA observations. These observations detect key emission lines, including [OII]$\lambda\lambda$ 3727, 3730, [OIII] 4364, [OIII] $\lambda\lambda$ 4960, 5008, [OIII] 88 $\mu$m, as well as H$\alpha$ and H$\beta$. JWST spectroscopy alone indicates interstellar medium (ISM) properties that are typical for galaxies at $z\sim7$. These include low dust extinction ($A_{\rm V} \approx 0.14$ mag), moderate electron density ($n_{\rm e} \approx 500$ cm$^{-3}$), and low gas-phase metallicity ($\sim10\%$). However, the strong far-infrared [OIII] 88 $\mu$m emission detected by ALMA cannot be explained by a single-phase ionized medium with uniform electron density and temperature. Instead, a two-phase ISM model, comprising compact, high-temperature, high-density gas components ($T_e \approx 26,000$ K; $n_e \approx 600 \mathrm{cm}^{-3}$) and an extended, cooler, lower-density component ($T_e \approx 8,000$ K; $n_e \approx 50 \mathrm{cm}^{-3}$), successfully reproduces the observed line ratios of [OIII] 88 $\mu$m/[OIII] 5008 \r{A} and [OIII] 4364 \r{A}/[OIII] 5008 \r{A}, with a volume ratio of 1 : 300 between the two phases. Our results demonstrate that JWST alone probes only a fraction of the ISM and highlight the critical importance of combining JWST and ALMA to reveal the density-stratified ISM of early galaxies.