CHEMICAL COMPARISON OF SAGITTARIUS AND FORNAX GLOBULAR CLUSTERS

Abstract

Both Sagittarius (Sgr) and Fornax have a complex structure and a system of globular clusters (GCs) at variance with the classic concept of dwarf spheroidal galaxies: simple, uniform spherical systems. Sgr and Fornax are of similar total mass but present great differences in some aspects. We compare the GCs of these two galaxies using the results from spectroscopic studies available in the literature. The Sgr GCs present a wide range in metallicity and they can be divided in two groups: young, metal-rich clusters with a red horizontal branch (HB) and old, metal-poor clusters with a blue HB. On the other hand, the Fornax clusters show similar metallicity and have essentially the same age (with the possible exception of cluster 4 that seems to be 3 Gyr younger) but have a wide range of HB types. The most metal-poor cluster in the Sgr system, Ter 8, has a metallicity comparable with the Fornax globular results. Oxygen and α-elements abundances of the Fornax clusters and the metal-poor Sgr globulars are similar and, with the metal-rich Sgr clusters, they appear to follow the same patterns found in Galactic GC stars. The behavior of the light and heavy s-process elements with the iron content shows analogous results for the Sgr metal-poor clusters and the Fornax clusters. We can say that the Sgr GCs are more like those in the Milky Way (MW) with a range in metallicities while Fornax clusters are more similar to the very outer MW clusters with second parameter problems.