Twins born in different environments? Nuclei of two dSphs: isolated galaxy KKS3 and E269-66, a close neighbor of NGC5128

摘要

We present the results of age, metallicity and radial velocity determination for central massive globular clusters (GCs) in dwarf spheroidal galaxies: KKs3 and ES0269-66. KKS3 is a unique isolated galaxy. ES0269-66 is a close neighbor of the giant SO Centaurus A. The results contribute to the knowledge about the origin of massive star clusters and their host dSphs. The structure and star formation histories of the two dwarf galaxies look rather similar. Both of them have experienced several star-forming events. The most recent ones occurred 1-2 Gyr ago, and most powerful bursts happened 12-14 Gyrs ago. Our analysis has shown that both GCs appear to be 1-2 Gyr younger and 0.1-0.3 dex more metal-rich than the most ancient metal-poor stars in the host dSphs. We examine signatures of multiple stellar population in the GCs using our data. Since central star-forming bursts were extended in time, the massive clusters might be considered as nuclei of the galaxies.