AI 中文总结
研究银河系和矮星系恒星中镁同位素比率，通过高分辨率和高信噪比光学光谱计算，发现给定[Fe/H]时两类恒星镁同位素比率有别，给定[Mg/H]时核合成过程一致，为化学演化模型提供新维度并助于限制大质量恒星核合成。
AI 中文摘要
在层级星系形成的假设下，矮星系是与合并形成银河系的高红移原星系最相似的现存天体。这些低质量系统是研究核合成通道的独特实验室，因其恒星化学成分对限制化学富集历史至关重要。目前矮星系恒星丰度几乎只关注元素丰度比，而同位素组成信息至关重要。我们利用高分辨率（65000 < R < 160000）和高信噪比（S/N > 250）的光学光谱计算了六颗吸积矮星系恒星（低α）和七颗银河系恒星（高α）的镁同位素比率。首次表明，在给定[Fe/H]时，矮星系中诞生的恒星与银河系中诞生的恒星镁同位素比率不同。但在给定[Mg/H]而非[Fe/H]比较同位素比率时，出现了一个有力诊断，表明核合成过程在不同恒星环境中是一致的。镁同位素丰度的这种普遍性为化学演化模型提供了额外维度，并有助于限制宇宙时间内大质量恒星的核合成。
英文摘要
Under the assumption of hierarchical galaxy formation, dwarf galaxies are the closest existing analogues to the high-redshift protogalaxies that merged to form the Milky Way. These low-mass systems serve as unique laboratories for studying nucleosynthetic channels, given that the chemical compositions of their stars play a pivotal role in constraining their chemical enrichment history. To date, stellar abundances in dwarf galaxies have focused almost exclusively on elemental abundance ratios. While important, elemental abundances omit critical information about the isotopic composition. Here, we compute the Mg isotopic ratios of six accreted dwarf galaxy stars (low-alpha) and seven Milky Way stars (high-alpha) using a set of high-resolution (65000 < R < 160000) and high signal-to-noise ratio (S/N > 250) optical spectra. We show, for the first time, that at a given [Fe/H], stars born in a dwarf galaxy differ in their Mg isotopic ratios from stars born in the Milky Way. However, when comparing isotopic ratios at a given [Mg/H] rather than [Fe/H], a powerful diagnostic emerges that suggests nucleosynthesis processes are consistent across different stellar environments. This universality of Mg isotopic abundances provides additional dimensionality for chemical evolution models and helps to constrain massive-star nucleosynthesis across cosmic time.
Comments7 pages, 3 figures, 2 tables. Published in MNRAS
Journal refMNRAS, 534, L35-L41 (2024)
