标题： 28个银河系球状星团中多重恒星种群的广域视图 显示英文标题

标题： A Wide-Field View on Multiple Stellar Populations in 28 Milky Way Globular Clusters

摘要： 银河系球状星团（GCs）中的大多数包含多个恒星种群，表现出特定的化学丰度变化。 特别是， GCs通常包含一个“原始”种群，其丰度类似于场星，以及一个“富集”种群，表现出轻元素异常。 在本文中，我们对28个银河系GC中的多个恒星种群进行了统一且全面的分析。 通过结合哈勃望远镜（HST）测光与广域地面测光，我们能够分析每个星团中84%到99%的所有恒星。 对于每个GC，我们使用已建立的 $C_{\rm{UBI}}$ 颜色指数将恒星分类为不同的子种群，并研究这些种群的空间分布。 我们的结果表明，动力学年轻的GC可以包含中心集中分布的富集或原始种群，或者没有中心集中分布的种群。 动力学古老的GC显示出完全混合的种群，如预期的那样。 那些最初就具有中心集中分布的原始 （并且均匀混合）种群的星团的存在加剧了许多星团形成情景面临的质量预算问题。 这些结果的多样性也突显了需要更多的理论来解释我们发现的初始条件的广泛多样性。 最后，我们研究了GC样本中不同全局参数下富集恒星的比例，并使用了来自大麦哲伦星云和小麦哲伦星云的年轻和低质量星团的数据，确认了早期的结果，即富集恒星的比例与星团的初始质量强烈相关。 显示英文摘要

摘要： The majority of Galactic globular clusters (GCs) contain multiple stellar populations displaying specific chemical abundance variations. In particular, GCs generally contain a `primordial' population with abundances similar to field stars, along with an `enriched' population exhibiting light element anomalies. In this paper we present a homogeneous and wide-view analysis of multiple stellar populations in 28 Galactic GCs. By using a combination of HST photometry together with wide-field, ground-based photometry we are able to analyse between 84% and 99% of all stars in each cluster. For each GC, we classify stars into separate sub-populations using the well-established $C_{\rm{UBI}}$ colour index, and investigate the spatial distributions of these populations. Our results show that dynamically young GCs can contain either centrally concentrated enriched or primordial populations, or no centrally concentrated population. Dynamically old GCs show fully mixed populations as expected. The existence of clusters born with centrally concentrated primordial (and homogeneously mixed) populations exacerbates the mass-budget problem facing many cluster formation scenarios. The diversity in these results also highlights the need for additional theories that can account for the wide variety of initial conditions that we find. We finally investigate the enriched star fraction as a function of different global parameters in our GC sample, using also data for young and low-mass clusters from the Small- and Large Magellanic Clouds and confirm earlier results that the enriched star fraction strongly correlates with the initial mass of a cluster.