标题： 从GTC/MEGARA和JWST/MIRI获得的IZw18中扩展的HeII电离的新线索 显示英文标题

标题： New clues on the extended HeII ionization in IZw18 from GTC/MEGARA and JWST/MIRI

摘要： IZw18是在z$\sim$0时已知的金属量最低的恒星形成星系之一，被认为是早期星系的独特本地类似物。 其硬电离连续谱的起源，预计是早期宇宙的普遍特征，并通过He\textsc{二}发射线进行追踪，仍然存在激烈争论且难以解释。 在这里，我们将光学（GTC/MEGARA）和中红外（JWST/MIRI）积分场光谱观测结果结合用于IZw18，以对高电离现象提供新的见解。 这封信报告了在IZw18中首次检测到高电离的[Ne\textsc{v}]14.32 $\mu$m线。 其发射具有空间扩展性，并与He\textsc{二}峰值重合，揭示了存在能量极高的电离源，这些源超越了仅基于He\textsc{二}提出的先前机制。 我们的运动学研究强调，He\textsc{二}$\lambda$ 4686发射气体表现出比H$\beta$发射更高的速度弥散和不同的速度模式，这表明存在诸如激波或恒星驱动的反馈等能量过程。 此外，综合光谱显示He\textsc{二}$\lambda$ 4686线中存在不对称的蓝移轮廓，可能表明存在\textbf{早期阶段}恒星驱动的外流，可能有助于未来的电离光子泄漏。 我们的空间分析还揭示了H$\beta$和He\textsc{二}$\lambda$ 4686发射之间的结构差异，其中He\textsc{二}$\lambda$ 4686峰值在投影距离上偏离H$\beta$峰值140 pc。 这表明最极端的电离源与中等电离源位于不同的位置。 我们的发现强调了极低金属环境中\textbf{高电离的}气体中物理过程的复杂相互作用，为早期星系中的条件提供了新的见解。 显示英文摘要

摘要： IZw18 is one of the lowest-metallicity star-forming galaxies known at z$\sim$0, considered a unique local analogue of the first galaxies. The origin of its hard ionizing continuum, expected to be a common feature in the early Universe and traced by He\textsc{ii} emission lines, remains intensely debated and challenging to explain. Here we combine optical (GTC/MEGARA) and mid-infrared (JWST/MIRI) integral field spectroscopic observations for IZw18 to shed new light on the high-ionization phenomenon. This letter reports the first detection of the high-ionization [Ne\textsc{v}]14.32 $\mu$m line in IZw18. Its emission is spatially extended and coincident with the He\textsc{ii} peak, revealing the presence of highly energetic ionizing sources that surpass mechanisms previously proposed on the basis of He\textsc{ii} alone. Our kinematic studies highlight that the He\textsc{ii}$\lambda$4686-emitting gas displays higher velocity dispersions and a different velocity pattern compared to the H$\beta$ emission, suggesting the presence of energetic processes such as shocks or stellar-driven feedback. Additionally, integrated spectra show asymmetric blueshifted profiles in the He\textsc{ii}$\lambda$4686 line, possibly indicating \textbf{early-stage} stellar-driven outflows potentially facilitating future ionizing photon leakage. Our spatial analysis also reveals differences in structure between the emission of H$\beta$ and He\textsc{ii}$\lambda$4686, with the He\textsc{ii}$\lambda$4686 peak offset by a projected distance of 140 pc from the peak H$\beta$ emission. This indicates distinct locations for the most extreme ionizing sources compared to moderate ionizing sources. Our findings underscore the complex interplay of physical processes in extremely metal-poor environments with \textbf{high-ionized} gas, offering new insights into the conditions prevailing in the early galaxies.