Lyα发射体的集体声音：来自JWST堆叠光谱的洞察
The Collective Voice of Ly$α$ Emitters: Insights from JWST Stacked Spectroscopy
AI总结：
研究利用JWST数据揭示了红移大于4的Lyα发射体的集体特性，发现Lyα逃逸分数随半径增加而上升，表明共振散射促进Lyα光子逃逸，同时揭示了低金属度和高电离参数等特征，指出反馈驱动的化学富集过程。
摘要：
我们利用JWST/NIRSpec棱镜光谱观测了287个红移大于4的Lyα发射体（LAEs），并对其进行空间分辨的堆叠分析。通过从公开调查（CAPERS、CEERS、JADES和RUBIES）中构建二维堆叠，我们探测了典型LAEs在亚千帕斯克尺度上的平均内部结构。我们发现共振发射与非共振发射之间存在明显的径向分离：虽然Hβ的等效宽度（EW）和其他光学线随半径增加而降低，但Lyα的等效宽度则向外围增加，且Lyα逃逸分数从中心的约16%增加到更大半径处的大于24%。这种行为表明，共振散射将Lyα光子重新分布到低密度的外围区域，其中逃逸变得更加高效。光学诊断和Te测量揭示了低金属度（12+log(O/H)≈7.7±0.2）、高电离参数、几乎没有尘埃消光以及系统性提高的N/O比（log(N/O)≈-0.4）。后者将典型LAEs置于氮增强的高红移星系中，指向快速且可能由反馈驱动的化学富集。推断的电离光子产生效率（log(ξion/HZerg⁻¹)≈25.2）以及高Lyα逃逸分数表明，这些系统是高效的，但并非极端的，离子光子预算贡献者。与SPICE辐射-流体动力学模拟的比较表明，爆发性超新星反馈模型自然再现了观测到的Lyα逃逸、紫外斜率和发射线等效宽度的径向趋势，将Lyα的空间再分布与随机星形成和反馈驱动的气体流动联系起来。我们的结果表明，在典型的红移大于4的LAEs中，Lyα发射、化学富集和反馈紧密相连。
英文摘要：
We present a spatially resolved stacked analysis of 287 LAEs at $z>4$ observed with JWST/NIRSpec prism spectroscopy. By constructing a two-dimensional stack from public surveys (CAPERS, CEERS, JADES, and RUBIES), we probe the average internal structure of typical LAEs on sub-kiloparsec scales. We find a clear radial decoupling between resonant and non-resonant emission: while EW(H$β$) and other optical lines decline with radius, EW(Ly$α$) increases toward the outskirts, and the Ly$α$ escape fraction rises from $\sim16\%$ in the center to $\gtrsim24\%$ at larger radii. This behavior suggests that resonant scattering redistributes Ly$α$ photons into lower-density outer regions, where escape becomes more efficient. Optical diagnostics and $T_e$ measurements reveal low metallicities ($12+\log(\rm O/H)\simeq7.7\pm0.2$), high ionization parameters, negligible dust attenuation, and systematically elevated N/O ratios ($\log({\rm N/O})\sim-0.4$). The latter place typical LAEs among the growing population of nitrogen-enhanced high-redshift galaxies, pointing to rapid and possibly feedback-driven chemical enrichment. The inferred ionizing photon production efficiency, $\log(ξ_{\rm ion}/{\rm Hz\,erg^{-1}})\simeq25.1-25.2$, together with the high Ly$α$ escape fractions, suggests that these systems are efficient, though not extreme, contributors to the ionizing photon budget. Comparison with SPICE radiation-hydrodynamic simulations shows that bursty supernova feedback models naturally reproduce the observed radial trends in Ly$α$ escape, UV slope, and emission-line equivalent widths, linking the spatial redistribution of Ly$α$ to stochastic star formation and feedback-driven gas flows. Our results demonstrate that Ly$α$ emission, chemical enrichment, and feedback are tightly connected in typical $z>4$ LAEs. (Shortened version for arXiv)
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