No evidence for multiple stellar populations in the low-mass Galactic globular cluster E 3

Abstract

Multiple stellar populations are a widespread phenomenon among Galactic globular clusters. Even though the origin of the enriched material from which new generations of stars are produced remains unclear, it is likely that self-enrichment will be feasible only in clusters massive enough to retain this enriched material. We searched for multiple populations in the low mass (M~1.4 x 10^4 M_sun) globular cluster E 3, analyzing SOAR/Goodman multi-object spectroscopy centered on the blue CN absorption features of 23 red giant branch stars. We find that the CN abundance does not present the typical bimodal behavior seen in clusters hosting multi stellar populations, but rather a unimodal distribution that indicates the presence of a genuine single stellar population, or a level of enrichment much lower than in clusters that show evidence for two populations from high-resolution spectroscopy. E 3 would be the first bona fide Galactic old globular cluster where no sign of self-enrichment is found.

v1: Submitted to ApJ on May 29 || v2: ApJ accepted (July 15). New high-resolution spectroscopy has been included giving a new radial velocity measurement of the cluster