大质量星系中硅丰度对第三族恒星的化学提示
Chemical hints of Population III stars from silicon abundances in massive galaxies
AI总结：
通过分析遗迹星系NGC 1277的深近红外光谱，发现异常高的硅与镁元素比([Si/Mg]=0.67)，表明早期存在极高质量、低金属丰度的前身星贡献，可能来自对不稳定超新星，为第三族恒星提供了化学证据。
摘要：
大质量星系的形成仍然是天体物理学中的一个基本问题，最近的JWST观测表明，剧烈的恒星形成发生得比以前预期的更早。我们使用典型的巨大遗迹星系NGC 1277作为化石记录来探测早期恒星形成的化学特征。NGC 1277的恒星质量为$1.2 \pm 0.4 \times 10^{11}M_\odot$，结构紧凑（半光半径1.2 kpc），代表了巨大遗迹星系——这些系统在高红移（$z>2$）时快速形成（“红核”），此后主要经历被动演化，保留了其最早恒星群的印记。通过深近红外光谱，我们在这个星系中识别出异常强的硅（Si）吸收特征。我们测得$[\mathrm{Si}/\mathrm{Fe}]=1.05^{+0.45}_{-0.27}$和$[\mathrm{Mg}/\mathrm{Fe}]=0.36^{+0.27}_{-0.24}$，对应显著增强的硅镁比（$[\mathrm{Si}/\mathrm{Mg}]=0.67^{+0.45}_{-0.27}$），这无法用当前的恒星群模型或典型的核塌缩超新星产额重现。这种增强表明在恒星形成的最早阶段存在极高质量、低金属丰度的前身星贡献。这样的条件与对不稳定超新星或其他与极高质量恒星相关的增丰通道的核合成产额一致，由于NGC 1277的快速形成时标和极少的后期吸积，这些化学特征在其中预期保持较少稀释。这一结果提供了局域遗迹星系中保存的早期大质量恒星增丰的罕见化学证据，并为宇宙化学演化开辟了新的观测窗口。
英文摘要：
The formation of massive galaxies remains a fundamental question in astrophysics, with recent JWST observations suggesting that intense star formation occurred earlier than previously expected. We used the prototypical massive relic galaxy NGC 1277 as a fossil record to probe the chemical signatures of early star formation. With a stellar mass of $1.2 \pm 0.4 \times 10^{11}M_\odot$ and a compact structure (half-light radius of 1.2 kpc), NGC 1277 is representative of massive relic galaxies-systems that formed rapidly at high redshifts ("red nuggets" at $z>2$) and have since undergone largely passive evolution, preserving the imprint of their earliest stellar populations. Using deep near-infrared spectroscopy, we identified unusually strong silicon (Si) absorption features in this galaxy. We measure $[\mathrm{Si}/\mathrm{Fe}]=1.05^{+0.45}_{-0.27}$ and $[\mathrm{Mg}/\mathrm{Fe}]=0.36^{+0.27}_{-0.24}$, corresponding to a significantly enhanced silicon-to-magnesium ratio ($[\mathrm{Si}/\mathrm{Mg}]=0.67^{+0.45}_{-0.27}$) which cannot be reproduced by current stellar population models or typical core-collapse supernova yields. This enhancement suggests a contribution from very massive, metal-poor progenitors during the earliest phases of star formation. Such conditions are consistent with nucleosynthetic yields from pair-instability supernovae or other enrichment channels associated with extremely massive stars, whose chemical signatures are expected to remain less diluted in systems like NGC 1277 due to their rapid formation timescales and minimal late-time accretion. This result provides rare chemical evidence of early massive-star enrichment preserved in a local relic galaxy and opens a new observational window into the chemical evolution of the Universe.
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