arXiv 2209.033762022-09astro-ph.GA

由VLT/MUSE和JWST/NIRISS识别的$z=4$强透镜低质量星系周围的富含金属的中性气藏

Metal-Enriched Neutral Gas Reservoir around a Strongly-lensed, Low-mass Galaxy at $z=4$ Identified by JWST/NIRISS and VLT/MUSE

Xiaojing Lin, Zheng Cai, Siwei Zou, Zihao Li, Zuyi Chen, Fuyan Bian, Fengwu Sun, Yiping Shu, Yunjing Wu, Mingyu Li, Jianan Li, Xiaohui Fan, J. Xavier Prochaska,… 展开作者

Xiaojing Lin, Zheng Cai, Siwei Zou, Zihao Li, Zuyi Chen, Fuyan Bian, Fengwu Sun, Yiping Shu, Yunjing Wu, Mingyu Li, Jianan Li, Xiaohui Fan, J. Xavier Prochaska, Daniel Schaerer, Stephane Charlot, Daniel Espada, Miroslava Dessauges-Zavadsky, Eiichi Egami, Daniel Stark, Kirsten K. Knudsen, Gustavo Bruzual, Jacopo Chevallard

备注：: 4 figures, 1 table; Accepted for Publication in the ApJL
DOI：: 10.3847/2041-8213/aca1c4

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摘要：

在$z\gtrsim4$对低质量、低金属量星系的直接观测为详细检查类似于再电离宇宙的源中的电离辐射、气流和金属富集提供了不可或缺的机会。结合詹姆斯韦伯太空望远镜（JWST），VLT/MUSE和ALMA，我们在$z=3.98$（也参见Vanzella et al. 2022）对一个强透镜的低质量（$\approx 10^{7.6}$ ${\rm M}_\odot$）星系进行了详细的观测。我们识别出该星系强窄星云发射，包括CIV $λ\lambda1548,1550$，HeII $\lambda1640$，OIII] $λ\lambda1661,1666$，[NeIII] $\lambda3868$，[OII] $\lambda3727$和Balmer系列氢，表明由大质量恒星提供动力的贫金属HII区（$\lesssim 0.12\ {\rm Z}_\odot$）。此外，我们检测到一个金属富集阻尼Ly $α$系统（DLA）与星系的HI柱密度为$N_{\rm{HI}}\approx 10^{21.8}$ cm $^{-2}$。伴生DLA的金属丰度可能达到超太阳金属丰度（${\gtrsim Z}_\odot$）。此外，由于JWST和引力透镜，我们在$z=4$的$\approx 100$ pc的空间分辨率下呈现了分辨的UV斜率（$β$）图，其中陡峭的UV斜率在三个恒星形成团块周围达到$β\approx -2.5$。结合低红移的类似物，我们的观察表明，低质量，低金属含量的星系，占主导地位的再电离，可能被包围的金属富集，中性气体云的高覆盖率。这意味着低质量星系的金属富集是高效的，并进一步支持在低质量星系中，只有一小部分电离辐射可以通过低柱密度中性气体的星际或环星系通道逃逸。

英文摘要：

Direct observations of low-mass, low-metallicity galaxies at $z\gtrsim4$ provide an indispensable opportunity for detailed inspection of the ionization radiation, gas flow, and metal enrichment in sources similar to those that reionized the Universe. Combining the James Webb Space Telescope (JWST), VLT/MUSE, and ALMA, we present detailed observations of a strongly lensed, low-mass ($\approx 10^{7.6}$ ${\rm M}_\odot$) galaxy at $z=3.98$ (also see Vanzella et al. 2022). We identify strong narrow nebular emission, including CIV $λ\lambda1548,1550$, HeII $\lambda1640$, OIII] $λ\lambda1661,1666$, [NeIII] $\lambda3868$, [OII] $\lambda3727$, and Balmer series of Hydrogen from this galaxy, indicating a metal-poor HII region ($\lesssim 0.12\ {\rm Z}_\odot$) powered by massive stars. Further, we detect a metal-enriched damped Ly$α$ system (DLA) associated with the galaxy with the HI column density of $N_{\rm{HI}}\approx 10^{21.8}$ cm$^{-2}$. The metallicity of the associated DLA may reach the super solar metallicity (${\gtrsim Z}_\odot$). Moreover, thanks to JWST and gravitational lensing, we present the resolved UV slope ($β$) map at the spatial resolution of $\approx 100$ pc at $z=4$, with steep UV slopes reaching $β\approx -2.5$ around three star-forming clumps. Combining with low-redshift analogs, our observations suggest that low-mass, low-metallicity galaxies, which dominate reionization, could be surrounded by a high covering fraction of the metal-enriched, neutral-gaseous clouds. This implies that the metal enrichment of low-mass galaxies is highly efficient, and further support that in low-mass galaxies, only a small fraction of ionizing radiation can escape through the interstellar or circumgalactic channels with low column-density neutral gas.

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