ESO452-SC11: The lowest mass globular cluster with a potential chemical inhomogeneity

Abstract

We present the largest spectroscopic investigation of one of the faintest and least studied stellar clusters of the Milky Way, ESO452-SC11. Using the Anglo-Australian Telescope AAOmega and Keck HIRES spectrographs we have identified 11 members of the cluster and found indications of star-to-star light element abundance variation, primarily using the blue cyanogen (CN) absorption features. From a stellar density profile, we estimate a total cluster mass of $(6.8\pm 3.4)\times 10^3$ solar masses. This would make ESO452-SC11 the lowest mass cluster with evidence for multiple populations. These data were also used to measure the radial velocity of the cluster ($16.7\pm 0.3$ km s${}^{-1}$) and confirm that ESO452-SC11 is relatively metal-rich for a globular cluster ([Fe/H]$=-0.81\pm 0.13$). All known massive clusters studied in detail show multiple populations of stars each with a different chemical composition, but many low-mass globular clusters appear to be chemically homogeneous. ESO452-SC11 sets a lower mass limit for the multiple stellar population phenomenon.

13 pages, 11 figures. Accepted for publication in MNRAS

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