一个由重度尘埃遮蔽星系驱动的致密、富金属吸收体：$z\sim7$处CGM增丰的直接证据
A dense, metal-rich absorber driven by a heavily dust-obscured galaxy: The direct evidence of CGM enrichment at $z\sim7$
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中文总结 AI 辅助
本研究发现z=7.03处由重度尘埃遮蔽星系ND1驱动的致密富金属CGM吸收体，通过JWST和NOEMA观测揭示外流输运金属，表明恒星形成反馈可高效污染早期宇宙的CGM/IGM。
中文摘要 AI 辅助
我们报告了在z=7.03处偶然发现的一个致密、富金属的星系周介质（CGM）吸收体，以及其宿主星系，该吸收体沿一条朝向红色类星体的视线方向被识别。该吸收体展现出迄今在z>5处观测到的最大静止系等值宽度和柱密度，追踪了一个富金属的气体晕。利用深度JWST/NIRSpec和NOEMA观测，我们表征了该吸收体的物理性质，并将其宿主星系ND1识别为一个剧烈恒星形成的星系，其碰撞参数异常接近，约为16千秒差距，该星系被重度尘埃遮蔽，以至于仅在NIRCam最长波段的探测中被发现。[OIII]$\lambda$5007、H$\alpha$和[CII]$\lambda 158\\,\mu$m发射线的探测将系统红移锚定在z~7.0321，揭示了吸收气体相对于宿主星系约50公里/秒的连贯蓝移，表明存在由外流驱动的金属向晕中的输运。外流速度与测得的柱密度相结合，意味着外流率$\dot{M}_{\rm out}=64 M_\odot\\,yr^{-1}$和质量载荷因子$\eta=3$，表明从尘埃遮蔽的星暴中发射出高能、化学增丰的风。虽然整体电离状态和[Mg/Fe]比值与经验宇宙演化趋势一致，但该吸收体展现出增强的碳氧比（[C/O]）。这种丰度模式暗示了第三星族恒星爆炸的核合成产率，并与宿主星系延伸至$z \gtrsim 8$的恒星形成历史相符，可能提供了原始金属增丰的罕见化石记录。我们的发现表明，强烈的恒星形成反馈可以迅速且高效地将CGM/IGM污染至再电离纪元。宿主星系的NIR暗性质进一步暗示，静止系紫外巡天可能系统性地遗漏了在早期宇宙中驱动CGM和IGM尺度金属增丰的尘埃源。
英文摘要
We report the serendipitous discovery of a dense, metal-enriched circumgalactic medium (CGM) absorber at z=7.03, together with its host galaxy, identified along the sightline toward a red quasar. The absorber exhibits the largest rest-frame equivalent widths and column densities observed to date at z>5, tracing a metal-enriched gaseous halo. Using deep JWST/NIRSpec and NOEMA observations, we characterize the absorber's physical properties and identify its host, ND1, as a vigorously star-forming galaxy at an exceptionally close impact parameter of ~16kpc, so heavily dust-obscured that it is detected only in the longest-wavelength NIRCam bands. Detections of [OIII]$λ$5007, H$α$, and [CII]$λ158\,μ$m emission anchor the systemic redshift to z~7.0321, revealing a coherent ~50km/s blueshift of the absorbing gas relative to the host, suggesting outflow-driven metal transport into the halo. The outflow velocity, combined with the measured column density, implies an outflow rate of $\dot{M}_{\rm out}=64 M_\odot\,yr^{-1}$ and a mass loading factor $η=3$, indicating an energetic, chemically-enriched wind launched from a dust-obscured starburst. While the overall ionization state and [Mg/Fe] ratio align with empirical cosmic evolutionary trends, the absorber displays an enhanced carbon-to-oxygen ([C/O]) ratio. This abundance pattern suggests the nucleosynthetic yields of Population~III stellar explosions, and aligns with the host's star-formation history extending to $z \gtrsim 8$, potentially offering a rare fossil record of primordial metal enrichment. Our findings demonstrate that intense star-formation feedback can rapidly and efficiently pollute the CGM/IGM well into the Epoch of Reionization. The NIR-dark nature of the host further implies that rest-UV surveys may systematically miss the dusty sources that drive CGM- and IGM-scale metal enrichment in the early Universe.
发表机构
- University of Toronto（多伦多大学）
- Dunlap Institute for Astronomy and Astrophysics（邓普天文学与天体物理研究所）
- University of Copenhagen（哥本哈根大学）
- Niels Bohr Institute（尼尔斯·玻尔研究所）
- Steward Observatory, University of Arizona（亚利桑那大学斯图尔德天文台）
- MIT Kavli Institute for Astrophysics and Space Research（麻省理工学院卡弗里天体物理学与空间研究学院）
- Massachusetts Institute of Technology（麻省理工学院）
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