Formation and evolution of globular clusters in the Galaxy and Magellanic Clouds

• Autor(a) principal: Dias, Bruno Moreira de Souza
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: http://www.teses.usp.br/teses/disponiveis/14/14131/tde-26082014-090039/
• topic: diagramas Hertzprung-Russell e cor-magnitude; Estrelas: abundâncias Estrelas: cinemática e dinâmica; Estrelas: População II; Estrelas: variáveis: RR Lyrae; Galáxia: aglomerados globulares; Galáxia: bojo; Galáxia: conteúdo estelar; Galáxia: evolução; Galáxia: formação; Galáxia: halo; Galáxias: aglomerados de estrelas: geral; Galaxies: star clusters: general; Galaxy: bulge; Galaxy: evolution; Galaxy: formation; Galaxy: globular clusters; Galaxy: halo; Galaxy: stellar contents; Hertzprung-Russell and colour-magnitude diagrams; Magellanic Clouds; Nuvens de Magalhães; Stars: abundances; Stars: kinematics and dynamics; Stars: Population II; Stars: variables: RR Lyrae

Globular clusters are tracers of the formation and evolution of their host galaxies. Kinematics, chemical abundances, age and position of the clusters allows tracing interactions between Milky Way and surrounding galaxies and outlines their chemical enrichment history. In this thesis we analyse mid-resolution spectra of about 800 red giant stars in 51 Galactic globular clusters. It is the first time that [Fe/H] and [Mg/Fe] derived in a consistent way are published for such a huge sample of globular clusters, almost 1/3 of the total number of catalogued clusters. Our metallicities are showed to be more precise than previous works based on mid-resolution spectroscopy. A turnover at [Fe/H] ~ -1.0 is found in the plot [Fe/H] vs. [Mg/Fe] for bulge and halo, although bulge seems to have a more metal-rich turnover, i.e, bulge has more efficient formation than the halo. Comparing the abundances with age the timescale for SNIa to start to become important is 1Gyr. [Fe/H] vs. age corroborates the different star formation efficiency of bulge and halo while [Mg/Fe] does not follow that. Halo was formed in mini halos or dwarf galaxies, and two multiple population clusters had their origin analysed to check it. M 22 seems to have been formed in the Milky Way while NGC 5824 possibly was originated in a dwarf galaxy, although our results are inconclusive for NGC 5824. The Galactic bulge seems to have been formed fast i.e., probably the oldest globular cluster is there. In fact HP 1 has a bluer horizontal branch than expected for its metallicity and we interpret that as an age effect. We determine its distance using light curves of variable stars in order to constrain future age determinations via colour-magnitude diagram. Finally, we investigate interaction between Milky Way and its neighbour galaxy SMC. We find that some star clusters are being stripped out of the SMC main body, which is consistent with tidal stripping scenario for the interaction between the galaxies, instead of ram pressure that would only affect gas.