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Multiple Stellar Populations in Globular Clusters of the Galactic Bulge

Presentation #150.09 in the session “Star Clusters: Galactic, Extragalactic & Simulated”.

Published onJan 11, 2021
Multiple Stellar Populations in Globular Clusters of the Galactic Bulge

We present photometric evidence for multiple stellar populations (MSPs) in 14 globular clusters toward the southern Galactic bulge. The photometric data come as part of the Blanco DECam Bulge Survey (BDBS; Rich et al. 2020), and constitute the largest homogeneously calibrated, de-reddened sample of southern Galactic bulge point sources to date. The survey data allow for the first systematic photometric study of bulge globular cluster MSPs of the depth and precision presented here. We identify cluster members using Gaia proper motion measurements, and then isolate red giant branch (RGB) stars using traditional r vs. u-r CMDs. We use the pseudo-color index Cuggi which is highly sensitive to light element abundance variations to create psuedo-CMDs which broaden, and in some cases split, the RGB. We identify multiple stellar populations by fitting Gaussian mixture models to the histogram of Cuggi values in each cluster RGB. We find that all clusters in the sample contain at least two stellar populations. We find a significant anticorrelation between stellar population ratio and the absolute magnitude of each cluster, in line with recent studies of halo globular clusters. Data used in this paper comes from the Blanco DECam Survey Collaboration and we gratefully acknowledge financial support from the National Science Foundation under grants AST-1413755 and AST-1412673.

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