z=6莱曼α发射体解析至秒差距尺度的解剖：极端紫外斜率、贫金属区域及可能泄漏的星团
Anatomy of a z=6 Lyman-α emitter down to parsec scales: extreme UV slopes, metal-poor regions and possibly leaking star clusters
AI总结：
本文利用JWST对红移6.14的引力透镜莱曼α发射体进行高分辨率观测，在秒差距尺度上揭示了极端紫外斜率的致密星团、可能的电离辐射泄漏及极贫金属区域，展示了强透镜效应对早期星系精细结构研究的关键作用。
摘要：
我们展示了对一个位于红移6.14、由哈勃前沿场星系团MACS J0416引力透镜放大（μ=17-21）的星系进行的详细JWST/NIRSpec和NIRCam分析。该目标星系整体上是一个典型的致密且紫外暗弱（M_UV=-17.8）的莱曼α发射体，但巨大的放大倍率使得我们能够详细刻画亚星系尺度（低至几个秒差距）的结构。利用高光谱分辨率光栅（G395H，R~2700）对显著的Hα、Hβ和[OIII]λλ4959,5007光学谱线进行了空间分辨观测，这些谱线具有大等值宽度，EW(Hβ+[OIII])≳1000 Å，以及较高的电离光子产生效率log(ξ_ion/erg^{-1}Hz)=25.2-25.7。NIRCam深场成像揭示了致密的静止系紫外亮区以及单个星团的存在，其有效半径R_eff=3-8 pc，质量M~2·10^5-5·10^6 M_⊙。这些星团以陡峭的紫外斜率β_UV≲-2.5为特征，在某些情况下与谱线发射的缺失相关联，表明可能存在电离辐射的泄漏，这一点也得到了莱曼α发射在距离系统红移约100 km s^{-1}处达到峰值的支持。虽然整个系统以低金属丰度为特征，约为0.1 Z_⊙，但NIRSpec-IFU图还揭示了一个低光度、贫金属区域的存在，其金属丰度Z≲2% Z_⊙，在NIRCam成像中几乎无法探测到；该区域与系统中紫外最亮的结构之一相距>200 pc，如果不是由于该系统的大放大倍率，它将因过于暗弱而无法被探测到。
英文摘要：
We present a detailed JWST/NIRSpec and NIRCam analysis of a gravitationally-lensed galaxy ($\rm μ=17-21$) at redshift 6.14 magnified by the Hubble Frontier Field galaxy cluster MACS J0416. The target galaxy is overall a typical compact and UV-faint ($\rm M_{UV}=-17.8$) Lyman-$α$ emitter, yet the large magnification allows the detailed characterization of structures on sub-galactic scales (down to a few parsecs). Prominent optical $\rm Hα$, $\rm Hβ$ and [OIII]$λ\lambda4959,5007$ lines are spatially resolved with the high spectral resolution grating (G395H, R~2700), with large equivalent widths, EW($\rm Hβ$+[OIII])$\gtrsim1000$ Å, and elevated ionising photon production efficiencies $\rm log(ξ_{ion}/erg^{-1}Hz)=25.2-25.7$. NIRCam deep imaging reveals the presence of compact rest-UV bright regions along with individual star clusters of $\rm R_{eff}=3-8~pc$ in size and $\rm M\sim2\cdot10^5-5\cdot10^{6}~M_\odot$ in mass. These clusters are characterised by steep UV slopes, $\rmβ_{UV}\lesssim-2.5$, which in some cases are associated with a dearth of line emission, indicating possible leaking of the ionizing radiation, as also supported by a Lyman-$\rm α$ emission peaking at $\rm \sim100~km~s^{-1}$ from the systemic redshift. While the entire system is characterised by low-metallicity, $\sim0.1~Z_\odot$, the NIRSpec-IFU map also reveals the presence of a low-luminosity, metal-poor region with $\rm Z\lesssim2\%~Z_\odot$, barely detected in NIRCam imaging; this region is displaced by $\rm >200~pc$ from one of the brightest structures of the system in UV, and would have been too faint to detect if not for the large magnification of the system.
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