Blanco DECam Bulge Survey (BDBS). VII. Multiple Populations in Globular Clusters of the Galactic Bulge
Blanco DECam Bulge Survey (BDBS). VII. Multiple Populations in Globular Clusters of the Galactic Bulge
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DOI：
10.3847/1538-4357/ac94c5
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发表时间：
2022-11
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通讯作者：
Justin A. Kader;C. Pilachowski;Christian I. Johnson;R. Rich;M. Young;I. Simion;W. Clarkson;S. Michael;A. Kunder;A. K. Vivas;A. J. Koch-Hansen;T. Marchetti
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作者：
Justin A. Kader;C. Pilachowski;Christian I. Johnson;R. Rich;M. Young;I. Simion;W. Clarkson;S. Michael;A. Kunder;A. K. Vivas;A. J. Koch-Hansen;T. Marchetti
我们目前的光度证据多个恒星种群（MP）在14个球状星团（GC）朝向南银河系的隆起。测光数据是布兰科DECam隆起调查的一部分，这是一个深，宽场近紫外近红外（ugrizY）调查的南银河系隆起。在这里，我们提出了第一个系统的研究隆起GC多个人口与深测光，包括u带，这是一个重要的指标，在恒星大气中的hoc轴承分子的丰度。我们使用盖亚EDR 3自行测量来识别星团成员，然后使用r与u-r色星等图来分离红巨星分支星。我们发现的证据表明，所有14个集群主机至少有两个人口，和NGC 6441，NGC 6626和NGC 6656似乎有至少三个人口。这些星团中的许多都不是哈勃太空望远镜（HST）调查的一部分，也没有全面的光谱分析，所以我们在几个星团中提出了MP的第一个证据。我们不仅发现第一代恒星的比例与星团绝对V星等之间有很强的相关关系，而且相关系数和星团间散射度与HST的结果相似。我们的地面数据比类似的HST观测延伸到更大的径向距离，从而能够可靠地估计每个星团中第一代恒星的全球比例。这项研究表明，地基U-波段测光提供的DECam将被证明是强大的，在解决GC的多个人口的研究。
We present photometric evidence for multiple stellar populations (MPs) in 14 globular clusters (GCs) toward the southern Galactic bulge. The photometric data come as part of the Blanco DECam Bulge Survey, which is a deep, wide-field near-UV-near-IR (ugrizY) survey of the southern Galactic bulge. Here, we present the first systematic study of bulge GC multiple populations with deep photometry including the u band, which is a crucial indicator of the abundance of CNO-bearing molecules in stellar atmospheres. We identify cluster members using Gaia EDR3 proper motion measurements, and then isolate red giant branch stars using r versus u − r color–magnitude diagrams. We find evidence suggesting all 14 clusters host at least two populations, and NGC 6441, NGC 6626, and NGC 6656 appear to have at least three populations. Many of these clusters are not part of the Hubble Space Telescope (HST) surveys nor do they have comprehensive spectroscopic analyses so we are presenting the first evidence of MPs in several clusters. Not only do we find a strong anticorrelation between the fraction of first-generation stars and cluster absolute V magnitude, but the correlation coefficient and cluster-to-cluster scatter are similar to the results obtained from HST. Our ground-based data extend to much larger radial distances than similar HST observations, enabling a reliable estimate of the global fraction of first-generation stars in each cluster. This study demonstrates that ground-based u-band photometry as provided by DECam will prove powerful in the study of multiple populations in resolved GCs.