I investigate the observational signatures of the formation of dark matter cores in dwarf galaxies. I adopt the paradigm where the energy from star formation feedback is injected into the orbits of dark matter particles, forming a constant density core consistent with observations of dwarf galaxies. Using physically motivated constraints I show there is ample feedback energy available given the average stellar mass of dwarf galaxies to form cores in $10^{8}$--$10^{11}$\thinspace M$_{\odot}$ halos, and predict the maximum core size as a function of stellar mass. I describe how observational features of the old stellar content of dwarf galaxies are due to this core formation paradigm. As both dark matter and stars are collisionless fluids, the stars responsible for the feedback form in the centres of dwarf galaxies and have their orbits grown by subsequent star formation. This will naturally lead to age and metallicity gradients, with the younger and more metal rich stellar population near the dwarf centres. This process also prevents the destruction of globular clusters by driving them out of the dwarf nucleus --- the decrease in central dark matter density reduces the strength of dynamical friction --- and increases the likelihood of being stripped onto the stellar halos of larger galaxies. It also offers a model for forming multiple populations in globular clusters, with the only assumption being that the source of the polluted gas resides within the dwarf progenitor. As the orbit of a globular cluster grows, it will experience multiple accretion events with each pass through the gas-rich galaxy centre. The simple accretion model exhibits two traits revealed from observations --- a short accretion timescale and a sensitive dependence on mass --- without requiring an exotic initial stellar mass function or the initial globular cluster mass function to be 10--25 times larger than at present. / Dissertation / Doctor of Philosophy (PhD)

Detailed chemical abundances of globular clusters in the Milky Way and M31 (the Andromeda Galaxy) are presented based on analyses of high resolution spectra. The unusual Milky Way cluster Palomar 1 (Pal 1) is studied through spectra of individual red giant branch stars; these abundances show that Pal 1 is not a classical globular cluster, and may have been accreted from a dwarf satellite of the Milky Way. The Milky Way globular clusters 47 Tuc, M3, M13, NGC 7006, and M15 are studied through their integrated light (i.e. a single spectrum is obtained for each cluster) in order to test high resolution integrated light analyses. The integrated abundances from these clusters reproduce the average abundances from individual stellar analyses for elements that do not vary within a cluster (e.g. Fe, Ca, and Ni). For elements that do vary within the clusters (e.g. Na and Mg) the integrated abundances fall within the observed ranges from individual stars. Certain abundance ratios are found to be extremely sensitive to uncertainties in the underlying stellar populations, such as input models, empirical relations to determine atmospheric parameters, interloping field stars, etc., while others (such as [Ca I/Fe I]) are largely insensitive to these effects. With these constraints on the accuracy and precision of high resolution integrated light analyses, detailed abundances are obtained for seven clusters in the outer halo of M31 that were recently discovered in the Pan-Andromeda Archaeological Survey (PAndAS) and are likely to have originated in dwarf galaxy satellites. Three clusters are relatively metal rich ([Fe/H] > −1.5) for their locations in the outer halo; their chemical abundances suggest that they likely originated in one or more fairly massive dwarf satellities. The other four are more metal-poor, and may have originated in less massive dwarf satellites. These results indicate that the Milky Way and M31 have both experienced some amount of accretion from dwarf satellites, though M31 may have had a more active accretion history. / Graduate

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. / Aglomerados globulares são traçadores da formação e evolução de suas galáxias. Cinemática, abundâncias químicas, idades e posições dos aglomerados permitem traçar interações entre Via Láctea e galáxias vizinhas e suas histórias de enriquecimento químico. Nesta tese analisamos espectros de média resolução de mais de 800 estrelas gigantes vermelhas em 51 aglomerados globulares Galácticos. É a primeira vez que [Fe/H] and [Mg/Fe] determinados de modo consistente são publicados para uma amostra desse porte, ~1/3 dos objetos catalogados. Nossas metalicidades são mais precisas que trabalhos anteriores similares. Uma quebra em [Fe/H] ~ -1.0 é encontrada no gráfico [Fe/H] vs. [Mg/Fe] para o bojo e halo, embora bojo parece ter uma quebra em [Fe/H] maior, i.e, bojo tem formaçãao mais eficiente que o halo. Comparando abundâncias com idade, a escala de tempo para SNIa ficar importante é 1Gano. [Fe/H] vs. idade corrobora diferentes eficiências de formação do bojo e halo, mas [Mg/Fe] vs. idade não mostra isso. O halo foi formado em mini halos ou galáxias anãs, e dois aglomerados com dispersão em [Fe/H] tiveram suas origens analisadas. M 22 parece ter sido formado na Via Láctea e NGC 5824 possivelmente foi originado em uma galáxia anã, embora os resultados são inconclusivos para NGC 5824. O bojo parece ter sido formado rapidamente e deve possuir o aglomerado mais velho. De fato, HP 1 tem um ramo horizontal mais azul que o esperado para sua metalicidade e vemos isso como um efeito da idade. Determinamos sua distância usando curvas de luz de RR Lyrae de maneira a restringir futuras determinações de idade via diagrama cor-magnitude. Finalmente, investigamos a interação entre Via Láctea e sua galáxia vizinha SMC. Encontramos aglomerados sendo removidos do corpo central da SMC, consistente com cenário de remoção por força de maré para a interação entre as galáxias, em vez de ``ram pressure\'\' que afeta só gás.

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. / Aglomerados globulares são traçadores da formação e evolução de suas galáxias. Cinemática, abundâncias químicas, idades e posições dos aglomerados permitem traçar interações entre Via Láctea e galáxias vizinhas e suas histórias de enriquecimento químico. Nesta tese analisamos espectros de média resolução de mais de 800 estrelas gigantes vermelhas em 51 aglomerados globulares Galácticos. É a primeira vez que [Fe/H] and [Mg/Fe] determinados de modo consistente são publicados para uma amostra desse porte, ~1/3 dos objetos catalogados. Nossas metalicidades são mais precisas que trabalhos anteriores similares. Uma quebra em [Fe/H] ~ -1.0 é encontrada no gráfico [Fe/H] vs. [Mg/Fe] para o bojo e halo, embora bojo parece ter uma quebra em [Fe/H] maior, i.e, bojo tem formaçãao mais eficiente que o halo. Comparando abundâncias com idade, a escala de tempo para SNIa ficar importante é 1Gano. [Fe/H] vs. idade corrobora diferentes eficiências de formação do bojo e halo, mas [Mg/Fe] vs. idade não mostra isso. O halo foi formado em mini halos ou galáxias anãs, e dois aglomerados com dispersão em [Fe/H] tiveram suas origens analisadas. M 22 parece ter sido formado na Via Láctea e NGC 5824 possivelmente foi originado em uma galáxia anã, embora os resultados são inconclusivos para NGC 5824. O bojo parece ter sido formado rapidamente e deve possuir o aglomerado mais velho. De fato, HP 1 tem um ramo horizontal mais azul que o esperado para sua metalicidade e vemos isso como um efeito da idade. Determinamos sua distância usando curvas de luz de RR Lyrae de maneira a restringir futuras determinações de idade via diagrama cor-magnitude. Finalmente, investigamos a interação entre Via Láctea e sua galáxia vizinha SMC. Encontramos aglomerados sendo removidos do corpo central da SMC, consistente com cenário de remoção por força de maré para a interação entre as galáxias, em vez de ``ram pressure\'\' que afeta só gás.