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arXiv 2402.01522astro-ph.GAastro-ph.SR
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银河系盘星族双红巨星分支与红团簇特征:基于Gaia GSPspec

Double Red Giant Branch and Red Clump features of Galactic disc stellar populations with Gaia GSPspec

Alejandra Recio-Blanco, P. de Laverny, P. A. Palicio, S. Cassisi, A. Pietrinferni, N. Lagarde, C. Navarrete

AI总结:

利用Gaia DR3 GSP-Spec高精度数据,首次在巨星基尔图中观测到银盘双峰性,表现为双红巨星分支和红团簇特征,揭示年龄间隙及复杂年龄-金属丰度关系,为理解银盘演化提供新视角。

摘要:

为厘清银河系演化中相互竞争的多种物理过程,需要对银盘双峰性进行详细的化学-运动学-动力学表征,并需具备高统计量。本文利用Gaia DR3 GSP-Spec恒星化学物理参数星表中一个极其精确的子样本。所选数据库包含408800颗恒星,其有效温度、表面重力对数值和金属丰度[M/H]的中位不确定度分别为10 K、0.03 dex和0.01 dex。恒星参数的精确性使得能够打破银盘恒星的年龄-金属丰度简并。首次在巨星基尔图(Kiel diagramme)中观测到银盘双峰性,并消除了星际消光问题。这种双峰性导致单金属丰度星族产生双红巨星分支序列和红团簇特征。与BaSTI等时线的比较表明,需要存在年龄间隙才能解释演化序列的分离,这与先前利用次巨星得到的年龄-金属丰度关系一致。在恒星质量-[α/Fe]平面中,在恒定金属丰度下观测到双峰分布。最后,对[M/H]=0.45±0.03 dex的恒星进行选择,结果显示银河系盘中最富金属的星族中,有相当比例恒星的年龄处于5-13 Gyr范围。这一古老、极富金属的星族可能是来自银河系内部区域的迁移恒星,以及银河系最后一次重大并合之前形成的古老盘恒星混合而成。Gaia GSP-Spec银盘单丰度星族的基尔图揭示了由银河系演化的内部和外部过程共同塑造的复杂、非线性的年龄-金属丰度关系。对其详细分析为重构银河系银盘双峰性之谜提供了新机遇。

英文摘要:

To disentangle the different competing physical processes at play in Galactic evolution, a detailed chrono chemicalkinematical, and dynamical characterisation of the disc bimodality is necessary, including high number statistics. Here we make use of an extremely precise subsample of the Gaia DR3 GSP-Spec catalogue of stellar chemophysical parameters. The selected database is composed of 408 800 stars with a median uncertainty of 10 K, 0.03 and 0.01 dex in Teff , log(g) and [M/H], respectively. The stellar parameter precision allows to break the age-metallicity degeneracy of disc stars. For the first time, the disc bimodality in the Kiel diagramme of giant stars is observed, getting rid of interstellar absortion issues. This bimodality produces double Red Giant Branch sequences and Red Clump features for mono-metallicity populations. A comparison with BaSTI isochrones allows to demonstrate that an age gap is needed to explain the evolutionary sequences separation, in agreement with previous age-metallicity relations obtained using sub-giant stars. A bimodal distribution in the stellar mass-[alpha/Fe] plane is observed at constant metallicity. Finally, a selection of stars with [M/H]=0.45 \pm 0.03 dex shows that the most metal-rich population in the Milky Way disc presents an important proportion of stars with ages in the range 5-13 Gyr. This old, extremely metal-rich population is possibly a mix of migrated stars from the internal Galactic regions, and old disc stars formed before the last major merger of the Milky Way. The Gaia GSP-Spec Kiel diagrammes of disc mono-abundance stellar populations reveal a complex, non linear age-metallicity relation crafted by internal and external processes of Galactic evolution. Their detailed analysis opens new opportunities to reconstruct the puzzle of the Milky Way disc bimodality.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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