AI 中文总结
本研究在EAGLE等四个宇宙学模拟及SDSS观测中检验基础金属丰度关系，发现大质量星系的金属丰度与比恒星形成率的反相关反转，该反转由强核外流驱动，为研究重子循环提供新框架。
AI 中文摘要
星系的金属含量为驱动星系演化的内在物理过程提供了直接线索，这方面的一个例子是恒星质量、气体相金属丰度与恒星形成率之间的三参数关系，通常被称为基础金属丰度关系（FMR）。此前研究表明，在红移z≲4的情况下，FMR具有红移不变性，且能完全解释质量-金属丰度关系（MZR）中的弥散。本研究在宇宙学模拟（EAGLE、SIMBA、Illustris、IllustrisTNG）与斯隆数字巡天（SDSS）观测中对这一“基础”关系进行了检验。我们发现，在EAGLE、IllustrisTNG和SDSS中，大质量星系（恒星质量M⋆≳10^10.5 M⊙）的金属丰度与比恒星形成率（sSFR）之间的典型反相关发生反转；当纳入低恒星形成星系时，所有四个模拟及SDSS中均出现正相关。我们推测，这种反转可能由强核外流（例如来自活动星系核或恒星反馈）驱动，这类外流会使恒星形成熄灭，同时优先将星系中心富集的气体排出。我们还发现，观测中多种金属丰度诊断方法均出现这种“反转”（具体细节取决于诊断方法），且在模拟中该反转持续到z~1。这些结果表明，这些强核外流对简单的气体调节器型模型提出了挑战，并为未来模拟与观测中检验重子循环模型提供了新框架。
英文摘要
The metal content of galaxies provides direct insight into the underlying physical processes that drive galaxy evolution. An example of this is the three-parameter relationship between stellar mass, gas-phase metallicity, and star formation rate, commonly referred to as the Fundamental Metallicity Relation (FMR). Previous studies have suggested that the FMR is redshift-invariant (at $z \lesssim 4$) and fully accounts for the scatter in the mass-metallicity relation (MZR). In this work, we test this 'fundamental' relation in both cosmological simulations (EAGLE, SIMBA, Illustris, IllustrisTNG) and Sloan Digital Sky Survey (SDSS) observations. We find that the canonical anti-correlation between metallicity and specific star formation rate (sSFR) inverts in massive galaxies ($M_\star \gtrsim 10^{10.5} \mathrm{M}_\odot$) in EAGLE, IllustrisTNG, and SDSS. When including lower star forming galaxies, the positive correlation appears for all four simulations and SDSS. We speculate that this inversion may being driven by strong nuclear outflows (from, e.g., active galactic nuclei or stellar feedback), which quench star formation while simultaneously expelling preferentially enriched gas from the center of the galaxy. We also find that this 'inversion' appears in a number of metallicity diagnostics in observations (though the details depend on diagnostic) and persists out to $z \sim 1$ in the simulations. These results demonstrate that these strong nuclear outflows challenge simple gas regulator-type models and provide a new framework to test models of the baryon cycle in both future simulations and observations.
Comments19 pages, 8 figures
