AbstractsAstronomy & Space Science

Chemical abundances and kinematic properties of Galactic globular clusters

by Nikolay M. Kacharov

Institution: Universität Heidelberg
Department: The Faculty of Physics and Astronomy
Degree: PhD
Year: 2015
Record ID: 1099571
Full text PDF: http://www.ub.uni-heidelberg.de/archiv/18256


High-resolution spectroscopic studies of globular clusters (GC) have been a major break-through in our understanding of these ancient stellar systems. The observations carried out in the last decade revealed a very heterogeneous population of objects – not only have GCs undergone a complex star formation history resulting in large chemical inhomogeneities common amongst all of them, but there are also non-negligible cluster-to-cluster differences in both chemistry and kinematics that are not yet fully understood. In this thesis, we present the first ever high-resolution studies of two poorly known GCs M75 and NGC4372. M75 is a massive, relatively metal-rich, outer halo GC with extremely broad horizontal branch. We found that, besides the typical light-element variations, it shows a marginal spread in metallicity and likely has a small s-process rich population. Surprisingly for its metallicity, the majority of the analysed stars lack s-process enrichment, which hints to a formation in an environment that built metals very quickly. On the other hand, NGC4372 is one of the most metal-poor GCs in the Galaxy. It is found in the inner halo and has experienced multiple disk crossings. The chemical analysis revealed it as a standard representative of the old, metal-poor halo group. More interesting are its structural and kinematic properties as the cluster has an unusually high intrinsic rotation for its metallicity and appears to be rotationally flattened. Furthermore, since GCs trace the chemical properties of their environment, the thesis also includes the first homogeneous study of the Galactic halo evolution of the poorly studied a element sulphur traced by GC stars covering a large metallicity span.