A MUSE view on the formation of multiple populations in Globular Clusters: Observational constraints from chemistry, binaries, and kinematics

作为积分场摄谱仪MUSE保证时间观测的一部分，我们在多个时期观测了26个银河球状星团（GC）的中心区域，从而收集了200多万个恒星光谱。这个宝贵的数据集已被我们的小组用来表征，例如，运动学，二元性和金属性的个别集群的属性。 球状星团的一个有趣的方面是所谓的多种群的存在。长期以来，GC一直被认为是由具有相同年龄和相同化学成分的恒星组成的单一恒星群的完美例子。然而，仔细观察，情况似乎更为复杂。它现在已经表明，几乎所有的GC年龄超过2 Gyrs包含多个人口，虽然与各种属性。属于不同种群的恒星的特征是某些元素的丰度不同（例如，N，O，Na），并遵循特定的相关性。通过结合从红巨星分支（RGB）恒星的光度颜色推断出的信息，从MUSE光谱的光谱特性，我们将调查包括在我们的调查中的GC种群的化学，运动学和二元性质。在第一次，我们将集中精力对NGC 1851，NGC 6752，NGC 7078和Omega Centauri这四个优先星团进行彻底的分析。 这一集群样本代表了与多个种群有关的不同现象，从由两个主要种群组成的“善意”GC到具有据称（NGC 1851）和确认（NGC 5139）铁扩散的更复杂的集群。在第二次，我们将对剩下的16个集群进行工作，我们需要对这些集群进行测光来分离人口。这些集群的工作包括优化RGB恒星分离到各自的人口，比较人口之间的二进制分数，并量化金属络合物集群中的铁扩散我们的工作将提供新的观测约束的关键方面，这将有助于更好地了解GC中多个人口的起源。 这仍然是一个公开的辩论，其中理论很多，并且均匀地表征种群的属性最有助于限制一些形成场景。

As part of the Guaranteed Time Observations with the integral field spectrograph MUSE, we have observed the central regions of 26 Galactic Globular clusters (GCs) at multiple epochs, thus collecting more than 2 million individual stellar spectra. This invaluable dataset has been used by our group to characterize, for example, kinematics, binarity, and metallicity properties of individual clusters. An intriguing aspect of globular clusters is the presence of so-called multiple populations. For a long time, GCs have been considered perfect examples of a single stellar population consisting of stars having the same age and the same chemical composition. However, upon closer inspection, the situation appears to be more complex. It has now been shown that almost all GCs older than 2 Gyrs contain multiple populations, albeit with various properties. The stars belonging to the different populations are characterized by varying abundances of certain elements (e.g., N, O, Na) following particular correlations. By combining the information inferred from the photometric colors of red giant branch (RGB) stars with their spectroscopic properties from the MUSE spectra, we will investigate the chemical, kinematic, and binary properties of the populations in GCs included in our survey. In a first time, we will focus our efforts to make a thorough analysis of four priority clusters, NGC 1851, NGC 6752, NGC 7078, and Omega Centauri. This sample of clusters is representative of different phenomena linked to multiple populations, ranging from ``bona fide'' GCs consisting of two main populations to more complex clusters with alleged (NGC 1851) and confirmed (NGC 5139) iron spreads. In a second time, we will work on the remaining 16 clusters for which we have the photometry needed to separate the population. Work on these clusters includes optimizing the separation of RGB stars into their respective populations, comparing binary fractions between populations, and quantifying iron-spread in metal-complex clusters Our work will provide new observational constraints on key aspects that will help to better understand the origin of multiple populations in GCs. This is still an open debate where theories are numerous and characterizing populations' properties homogeneously is most helpful to constrain some of the formation scenarios.