Title Cheminė kinematiškai identifikuotos Galaktikos žvaigždžių grupės sudėtis /
Translation of Title Chemical composition of kinematically identified galactic stellar group.
Authors Stonkutė, Edita
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Pages 95
Keywords [eng] Galaxy evolution ; formation ; stars ; abundance
Abstract [eng] A number of stellar streams, moving and kinematic groups were identified in the Milky Way galaxy. Some of them are suspected to originate from accreted satellites. Can we also find such traces of ancient merger events in the solar neighbourhood? Helmi et al. (2006) identified three new coherent groups of stars in the Geneva-Copenhagen survey (Nordström et al. 2004) and suggested that those might correspond to remains of disrupted satellites. With the detailed chemical composition analysis of the newly identified kinematic group we aim to contribute to the Galactic substructure studies. The main aim of the study is to perform a high-resolution spectroscopic elemental abundance analysis in stars belonging to one of the newly identified kinematic groups and to compare the results with other stars in the Galactic disc. We performed the detailed chemical analysis of 21 stars attributed to Group 3 of the Geneva-Copenhagen survey and six comparison Galactic thin disc stars. The main atmospheric parameters and abundances of 22 chemical elements were determined. All programme stars are overabundant in oxygen and α-elements compared with the Galactic thin-disc. This abundance pattern has similar characteristics to those of the Galactic thick disc. The abundances of chemical elements produced predominantly by the r-process are overabundant in comparison with Galactic thin-disc dwarfs of the same metallicity. The abundances of iron-group elements and chemical elements produced mainly by the s-process are similar to those in the Galactic thin-disc dwarfs of the same metallicity. The chemical composition of stars in Group 3 is similar to the thick-disc stars, which might suggest that their formation histories are linked. The chemical composition together with the kinematic properties and ages of stars in the investigated Group 3 of the Geneva-Copenhagen survey support a gas-rich satellite merger scenario as the most suitable origin for Group 3.
Type Doctoral thesis
Language Lithuanian
Publication date 2013