The massive M31 cluster G1: detailed chemical abundances from integrated light spectroscopy★

ABSTRACT G1, also known as Mayall II, is one of the most massive star clusters in M31. Its mass, ellipticity, and location outer halo make it a compelling candidate for former nuclear cluster. This paper presents an integrated light abundance analysis based on moderately high-resolution (R = 15 000) spectrum obtained with spectrograph Hobby–Eberly Telescope 2007 2008. To independently determine metallicity, moderate-resolution ∼ 4000) Ca ii triplet lines near-infrared was Astrophysical Research Consortium’s 3.5-m telescope at Apache Point Observatory. From spectrum, G1 found to be metal-poor cluster, $[\rm {Fe/H}]~=~-0.98\pm 0.05$. shows signs α-enhancement (based Mg, Ca, Ti) lacks s-process enhancements seen dwarf galaxies comparisons Y, Ba, Eu), indicating that originated fairly galaxy. Intriguingly, exhibits Na Al enhancement, unique signature GCs – which suggests G1’s formation intimately connected GC formation. high [Na/Fe] extends previous trends cluster velocity dispersion even higher mass regime, implying are more able retain Na-enhanced ejecta. The effects intracluster spreads discussed subsequent paper. Ultimately, chemical properties resemble other M31 GCs, though shares some similarities extragalactic clusters.