arXiv 2501.095582025-01-16astro-ph.GA

利用MUSE开展球状星团恒星普查：第一代恒星中的金属度展宽与弥散

A stellar census in globular clusters with MUSE. Metallicity spread and dispersion among first-population stars

M. Latour, S. Kamann, S. Martocchia, T. -O. Husser, S. Saracino, S. Dreizler

备注：: Accepted for publication in Astronomy and Astrophysics
发表信息：: A&A 694, A248 (2025)
DOI：: 10.1051/0004-6361/202452420

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AI总结：

该研究基于MUSE对21个银河系球状星团8000余颗RGB恒星的光谱，结合HST伪色划分P1、P2星族，测得金属度展宽与弥散均随星团质量变化，支持自增丰模型。

摘要：

在银河系年老而大质量的球状星团（GC）中，多星族现象普遍存在。它们在一个球状星团形成过程中如何产生，目前仍不清楚。随着对银河系球状星团原始星族（P1）恒星中铁元素变化的测量，铁及金属度变化这一课题近来受到关注。我们使用MUSE观测的21个银河系球状星团中8000多颗红巨星支（RGB）恒星的光谱，推导每颗恒星的金属度[M/H]。对于每个星团，我们利用HST测光目录将恒星划分为两个主要星族（P1和P2）。通过将我们的金属度测量结果与恒星的$Δ_{\ m F275W,F814W}$伪色相结合，我们测量了每个星团原始星族内部的金属度展宽。我们还推导了每个球状星团P1和P2恒星的金属度弥散（$σ_{\ m [M/H]}$）。在除三个球状星团之外的所有星团中，我们测得P1恒星的金属度与$Δ_{\ m F275W,F814W}$伪色之间存在显著相关，即$Δ_{\ m F275W,F814W}$较大的恒星具有更高的金属度。我们测得的金属度展宽范围为0.03至0.24 dex，并与球状星团质量相关。至于内禀金属度弥散，当合并P1和P2恒星时，我们测得的数值范围为0.02 dex至0.08 dex，并且与球状星团质量具有非常好的相关性。我们比较了P1和P2恒星之间的金属度弥散，发现P2恒星的金属度弥散小于或等于P1恒星。我们发现，P1恒星的金属度展宽（来自染色体图中的$Δ_{\ m F275W,F814W}$展宽）和金属度弥散（$σ_{\ m [M/H]}$）都与球状星团质量相关，这与文献中提出的一些理论自增丰模型的预测一致。

英文摘要：

Multiple populations are ubiquitous in the old massive globular clusters (GCs) of the Milky Way. It is still unclear how they arose during the formation of a GC. The topic of iron and metallicity variations has recently attracted attention with the measurement of iron variations among the primordial population (P1) stars of Galactic GCs. We use the spectra of more than 8000 RGB stars in 21 Galactic GCs observed with MUSE to derive individual stellar metallicities [M/H]. For each cluster, we use the HST photometric catalogs to separate the stars into two main populations (P1 and P2). We measure the metallicity spread within the primordial population of each cluster by combining our metallicity measurements with the stars $Δ_{\rm F275W,F814W}$ pseudo-color. We also derive metallicity dispersions ($σ_{\rm [M/H]}$) for the P1 and P2 stars of each GC. In all but three GCs, we measure a significant correlation between the metallicity and the $Δ_{\rm F275W,F814W}$ pseudo-color of the P1 stars such that stars with larger $Δ_{\rm F275W,F814W}$ have higher metallicities. We measure metallicity spreads that range from 0.03 to 0.24 dex and correlate with the GC masses. As for the intrinsic metallicity dispersions, when combining the P1 and P2 stars, we measure values ranging from 0.02 dex to 0.08 dex that correlate very well with the GC masses. We compared the metallicity dispersion among the P1 and P2 stars and found that the P2 stars have metallicity dispersions that are smaller or equal to that of the P1 stars. We find that both the metallicity spreads of the P1 stars (from the $Δ_{\rm F275W,F814W}$ spread in the chromosome maps) and the metallicity dispersions ($σ_{\rm [M/H]}$) correlate with the GC masses, as predicted by some theoretical self-enrichment models presented in the literature.

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