Sökning: "galactic evolution"
Visar resultat 11 - 15 av 47 avhandlingar innehållade orden galactic evolution.
11. The nature of kinematic structures in the Galactic disc
Sammanfattning : The velocity distribution of stars in the Galactic disc is complex and consists of a vast number of kinematic structures, that is, stars that share similar velocity components. The reasons why some stars move together may be different and are related to dynamical processes connected to the Galaxy, both internal as well as external ones, such as resonances with the Galactic bar or the Galactic spiral arm structure, dissolution of open clusters, or merger events with other galaxies. LÄS MER
12. Studies of Interstellar Molecular Gas in the Magellanic Clouds
Sammanfattning : Results of observational studies of interstellar molecular gas clouds in the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC), two nearby metal-poor and dust-poor dwarf galaxies, are presented. Spectral line radiation emitted by interstellar molecules has been used to probe the physical state and the chemical composition of individual molecular clouds. LÄS MER
13. Determination of stellar ages and star formation histories - a Bayesian approach With an application to nearby F and G stars
Sammanfattning : In order to understand the formation and evolution of the Galaxy it is imperative to know when different components formed. This means at the most basic level that we need to know the ages of stars. The present work demonstrates the many problems inherent in determining the ages of stars through comparison with stellar evolutionary models. LÄS MER
14. Chemical Abundance Analysis of Population II Stars : The Summary Includes a Background in General Astronomy
Sammanfattning : We are made of stardust in the sense that most atomic nuclei around us have been formed by stars. Stars synthesise new elements and expel them to the interstellar medium, from which later new generations of stars are born. We can map this chemical evolution by analysing the atmospheric contents of old Galactic halo stars. LÄS MER
15. On the Abundances of Li, Be and O in Metal-Poor Stars in the Galaxy
Sammanfattning : Stellar atmospheres constitute excellent environments to study the chemical evolution of our Galaxy. The chemical composition of these atmospheres reflects the composition of the gas from where these stars were born. LÄS MER