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

TL;DR

This study investigates the faint, low-mass globular cluster ESO452-SC11, revealing potential chemical inhomogeneity and establishing it as the lowest mass cluster with evidence of multiple stellar populations.

Contribution

It provides the first detailed spectroscopic analysis of ESO452-SC11, demonstrating star-to-star chemical variations at very low cluster mass.

Findings

Detected light element abundance variations among members.

Estimated cluster mass of approximately 6,800 solar masses.

Confirmed the cluster's relatively high metallicity ([Fe/H] = -0.81).

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 $(6.8\pm3.4)\times10^3$ 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 ($16.7\pm0.3$ km s$^{-1}$) and confirm that ESO452-SC11 is relatively metal-rich for a globular cluster ([Fe/H]$=-0.81\pm0.13$). 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.