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(2014) Mark abstract Astronomers have already gained a lot of insight into the formation and evolution of galaxies, such as our own Milky Way. Nevertheless, there are still many mysteries that keep puzzling us. In this thesis we have explored galaxies in various ways, with the objective to better interpret the observations and to improve our understanding of the physical properties of galaxies and their substructures. The first part focuses on the stellar kinematics of early-type galaxies. The velocity dispersion (quantifying the internal speeds of the stars within a galaxy) is an important parameter in extragalactic scaling relations. However, we know that dust blocks and scatters the optical light of stars. Therefore, the determination of the velocity dispersion based on optical data could be unreliable. We address this problem by comparing optical velocity dispersions with velocity dispersions based on near-infrared data: this wavelength regime is much less affected by the complications introduced by the dust. We conclude that the optically-determined velocity dispersions for early-type galaxies are reliable, hence we can continue to use this parameter in extragalactic scaling relations. In the second part of this thesis we investigate the globular clusters of our own galaxy, the Milky Way. These clusters are fossil records of the early formation of galaxies and are therefore very important in the study of the formation and evolution of galaxies. We have observed the bulk of those clusters with the new standard optical SDSS filter set during a large observational campaign. We determined the magnitudes and colours of each object and corrected for Galactic foreground stars which do not belong to the cluster itself. We related these clean colours to the metallicity (chemical properties) of these star clusters and demonstrated that the dust in the Milky Way disk complicates the determination of accurate optical colours. Moreover, we fitted theoretical models to surface brightness profiles that reveal the structure of the clusters and we can associate these characteristics with the cluster position within the Milky Way and with the age of the cluster.

Please use this url to cite or link to this publication: http://hdl.handle.net/1854/LU-4306662

Autor: Joachim Vanderbeke

Fuente: https://biblio.ugent.be/publication/4306662


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