标题： 球状星团Liller 1中多铁子群体的首次证据 显示英文标题

标题： First evidence of multi-iron sub-populations in the Bulge Fossil Fragment candidate Liller 1

摘要： 在一项旨在表征所谓银晕化石碎片（银晕形成时期的化石残余）特性的项目背景下，我们在此首次确定了Liller 1的金属丰度分布。 对于64颗单个成员星的样本，我们使用ESO-MUSE光谱测量了CaII三重线的等值宽度，然后推导出铁的丰度。 为了测试所采用校准在富金属区域的有效性，该方法首先应用于三个参考银晕球状星团（NGC 6569、NGC 6440和NGC 6528）。 在所有三种情况下，我们发现单一成分的铁分布，其丰度值与文献中报告的结果完全一致。 然而，将相同的方法应用于Liller 1时，得到了明显的双峰铁分布，其中有一个低于太阳金属丰度的成分位于$\text{[Fe/H]}= -0.48\,$dex（$\sigma = 0.22$），一个高于太阳金属丰度的成分位于$\text{[Fe/H]}= +0.26\,$dex（$\sigma = 0.17$）。 后者被发现比贫金属群体更显著地集中在中心，这符合自增丰情景，并且与在另一个银晕系统Terzan 5中发现的结果一致。 获得的金属丰度分布与Liller 1的重建恒星形成历史所预测的惊人相似，该历史特征是三次主要爆发以及在整个生命周期中低但恒定的恒星形成活动。 这些发现进一步支持了这样的可能性，即类似于Terzan 5，Liller 1也是一个银晕化石碎片。 显示英文摘要

摘要： In the context of a project aimed at characterizing the properties of the so-called Bulge Fossil Fragments (the fossil remnants of the bulge formation epoch), here we present the first determination of the metallicity distribution of Liller 1. For a sample of 64 individual member stars we used ESO- MUSE spectra to measure the equivalent width of the CaII triplet and then derive the iron abundance. To test the validity of the adopted calibration in the metal-rich regime, the procedure was first applied to three reference bulge globular clusters (NGC 6569, NGC 6440, and NGC 6528). In all the three cases, we found single-component iron distributions, with abundance values fully in agreement with those reported in the literature. The application of the same methodology to Liller 1 yielded, instead, a clear bimodal iron distribution, with a sub-solar component at $\text{[Fe/H]}= -0.48\,$dex ($\sigma = 0.22$) and a super-solar component at $\text{[Fe/H]}= +0.26\,$dex ($\sigma = 0.17$). The latter is found to be significantly more centrally concentrated than the metal-poor population, as expected in a self-enrichment scenario and in agreement with what found in another bulge system, Terzan 5. The obtained metallicity distribution is astonishingly similar to that predicted by the reconstructed star formation history of Liller 1, which is characterized by three main bursts and a low, but constant, activity of star formation over the entire lifetime. These findings provide further support to the possibility that, similar to Terzan 5, also Liller 1 is a Bulge Fossil Fragment.