Detailed abundance analysis of globular clusters in the Local Group

Abstract

Context. Globular clusters (GCs) are emerging as powerful tracers of the chemical composition of extragalactic stellar populations. Aims. We present new abundance measurements for 11 GCs in the Local Group galaxies NGC 147, NGC 6822, and Messier 33. These are combined with previously published observations of four GCs in the Fornax and Wolf-Lundmark-Melotte (WLM) galaxies. Methods. The abundances were determined from analyses of integrated-light spectra obtained with the HIRES spectrograph on the Keck I telescope and with UVES on the Very Large Telescope (VLT). We used our analysis technique that was developed for this purpose and tested on Milky Way GCs. Results. We find that the clusters with [Fe/ H] -1.5, the GCs in M33 are also α-enhanced, while the GCs that belong to dwarfs (NGC 6822 SC7 and Fornax 4) have closer to solar-scaled α-element abundances. The abundance patterns in SC7 are remarkably similar to those in the Galactic GC Ruprecht 106, including significantly subsolar [Na/ Fe] and [Ni/ Fe] ratios. In NGC 147, the GCs with [Fe/ H]