光学错觉：高电子密度制造了极贫金属星系的假象

韦布空间望远镜（JWST）发现的许多极贫金属星系（EMPGs）可能因未考虑高电子密度而导致金属丰度被低估。本研究通过对Abell 2744引力透镜场中样本的分析，揭示了高电子密度会抑制特定谱线，从而造成星系金属丰度极低的假象。这一发现对准确理解早期宇宙的化学增丰过程具有重要意义。

arXiv:2608.20339v1 Announce Type: new Abstract: JWST has enabled the discovery of dozens of extremely metal-poor galaxies (EMPGs) with metallicities below $5\%\,Z_{\odot}$, representing a significant leap toward detecting the first galaxies without metals. However, accurate metallicity measurements require careful determination of physical conditions in the ionized gas. In this paper, we study four galaxies that appear to be EMPGs when analyzed using the direct $T_e$ method with the common low-density assumption ($n_e=10^3\,{\rm cm}^{-3}$). To test whether their metal-poor status holds when accurately measuring the density, we apply the direct method with a self-consistent determination of electron temperature ($T_e$) and density ($n_e$) in the high-ionization zone using the [OIII]$\lambda$5008, [OIII]$\lambda$4364, and [OIII]$\lambda$1666 lines, using JWST/NIRSpec data from the SPURS program in the Abell 2744 lensed field. We find that three out of four galaxies in our sample have extremely high electron densities ($n_e \sim 10^{5}-10^{6}\,{\rm cm^{-3}}$), which suppress the [OIII]$\lambda$5008 line and lead to underestimates of metallicity by up to $\sim1.1\,$dex when this density is not accounted for, and have true metallicities of 12+log(O/H) $\sim7.3-8.2$. Failure to account for high densities can therefore lead to systematic misclassification of metal-poor galaxies and biased conclusions about early chemical enrichment.