The peculiar chemical inventory of NGC2419: An extreme outer halo "globular Cluster"

Abstract

NGC2419 is a massive outer halo Galactic globular cluster (GC) whose stars have previously been shown to have somewhat peculiar abundance patterns. We have observed seven luminous giants that are members of NGC2419 with Keck/HIRES at reasonable signal-to-noise ratio. One of these giants is very peculiar, with an extremely low [Mg/Fe] and high [K/Fe] but normal abundances of most other elements. The abundance pattern does not match the nucleosynthetic yields of any supernova model. The other six stars show abundance ratios typical of inner halo Galactic GCs, represented here by a sample of giants in the nearby GC M30. Although our measurements show that NGC2419 is unusual in some respects, its bulk properties do not provide compelling evidence for a difference between inner and outer halo GCs. © 2011. The American Astronomical Society. All rights reserved.