AI 中文总结
研究发现 [Ce/Mg] 随金属丰度、银盘位置变化，并非通用化学钟，其模式反映本地恒星形成历史与AGB核合成，动摇了化学钟作为恒星年龄估算工具的通用性。
AI 中文摘要
s-过程元素与α元素的丰度比（[s/α]）被提出作为一种“化学钟”，即用于估算恒星年龄的工具。然而，年龄-[s/α]关系会随金属丰度和银河系位置变化，且观测到的趋势未被银河系化学演化模型很好地预测。我们利用 SDSS-V 银河系测绘巡天中 APOGEE 观测的约 10 万颗红巨星，量化了银河系银盘上年龄-[Ce/Mg]的相关性。我们发现，化学薄盘中该相关性的斜率会随金属丰度和引导半径显著变化：外银盘且金属丰度低于太阳的区域斜率最陡，而金属丰度最高的恒星和内银盘的恒星则未表现出与年龄的相关性。相比之下，化学厚盘中的 [Ce/Mg] 模式在整个银河系中一致。晕星的 [Ce/Mg] 高于化学厚盘，这表明渐近巨分支（AGB）星的增丰在低金属丰度环境中也很重要。总体而言，[Ce/Mg] 的模式既反映了本地恒星形成历史，也反映了 AGB 核合成。[Ce/Mg]、年龄、金属丰度和银河系位置之间的复杂相互作用意味着 [Ce/Mg]（以及延伸的 [s/α]）并非通用化学钟。
英文摘要
The ratio of $s$-process to $α$-element enrichment ($[s/α]$) has been proposed as a ``chemical clock,'' or a means to estimate stellar ages. However, the age--$[s/α]$ relation varies with metallicity and location in the Galaxy, and the observed trends are not well predicted by galactic chemical evolution models. We quantify the age--[Ce/Mg] correlation across the Galactic disk in roughly 100,000 red giant stars observed with APOGEE in the SDSS-V Milky Way Mapper survey. We find that the slope of the correlation varies significantly with metallicity and guiding radius in the chemical thin disk. The trend is steepest in the outer disk and below Solar metallicity, while the most metal-rich stars and those in the inner disk show no correlation with age. In contrast, [Ce/Mg] patterns in the chemical thick disk are consistent across the Galaxy. Halo stars have higher [Ce/Mg] than the chemical thick disk, suggesting that asymptotic giant branch (AGB) enrichment is important even at low metallicity. Overall, patterns in [Ce/Mg] trace both the local star formation history and AGB nucleosynthesis. The complex interplay between [Ce/Mg], age, metallicity, and Galactic position means that [Ce/Mg] (and by extension $[s/α]$) is not a universal chemical clock.
Comments24 pages, 17 figures; submitted to AAS journals
