Análise de idades e metalicidades de aglomerados estelares nas Nuvens de Magalhães traz informação para estudos sobre a evolução química e dinâmica das Nuvens. Usando-as como calibradores de modelos de populações estelares simples, esse tipo de análise é útil também para o estudo de outras galáxias. Um dos objetivos deste trabalho é derivar idades e metalicidades a partir de espectros integrados de 14 aglomerados na Pequena Nuvem de Magalhães. Busca-se o entendimento, em particular, dos aglomerados de idade intermediária/velha. A metodologia usada para isso é baseada em ajuste de espectro completo dos espectros integrados dos aglomerados, comparando-os a três bases de modelos de populações estelares simples; são usados dois códigos disponíveis na literatura para efetuar tais comparações. Desse modo, são identicados 9 aglomerados como de idade intermediária/velha e os outros 5, jovens. Destacam-se os resultados para os aglomerados com idade intermediária/velha recém identicadas: HW 1, NGC 152, Lindsay 3, 11 e 113. São conrmadas também as idades velhas de NGC 361, 419 e Kron 3 e do bem conhecido e mais velho aglomerado da Pequena Nuvem, NGC 121. Outro objetivo é determinar parâmetros físicos autoconsistentes (idade, metalicidade, distância e avermelhamento) para 7 aglomerados relativamente pouco estudados da Pequena Nuvem, com idades entre ~ 0.5 e 5 Ganos. Para isso são usadas ferramentas estatísticas que comparam CMDs modelados com os observados. Diferentemente de um ajuste visual de isócrona, essa abordagem oferece um critério objetivo e inequívoco para estabelecer quais são os CMDs sintéticos que melhor ajustam o CMD observado. Resultados preliminares mostram a eciência deste método, que determina log(idade), com incerteza de 0.10 e [Fe/H], com 0.20. Isso pode introduzir novos e importantes limites na relação idade-metalicidade da Pequena Nuvem, que é signicativamente mais complexa e menos estudada que a da Grande Nuvem. / Analysis of age and metallicity of star clusters in Magellanic Clouds brings information to studies on the chemical evolution and dynamics of the Clouds. By using them as calibrators of single stellar populations models, this type of analysis is also useful for the study of other galaxies. One of the aims of this work is to derive ages and metallicities from integrated spectra of 14 clusters in the Small Magellanic Cloud. We seek for the understanding, in particular, of the intermediate/old age clusters. The method used for this purpose is based on full spectrum tting of integrated spectra of the clusters, comparing them to three sets of single stellar populations; two codes available in the literature are used to do such comparisons. Thus 9 clusters are identied as intermediate/old age clusters and 5 other as young ones. Noteworthy are the results for the clusters with intermediate/old age newly identied: HW 1, NGC 152, Lindsay 3, 11 and 113. We also conrm the old ages of NGC 361, 419 and Kron 3, and of the well-known oldest cluster of the Small Cloud, NGC 121. Another aim is to determine self-consistent physical parameters (age, metallicity, distance and reddening) for 7 relatively unstudied stellar clusters in the Small Magellanic Cloud, with ages between 0.5 and 5 Gyr. We use statistical tools to compare synthetic and observed CMDs. Dierently of a visual isochrone t, this approach oers ob jective and unambiguous criteria to establish which are the synthetic CMDs that best ts the observed CMD. Preliminary results show the eciency of this method, which determines log(age), with an uncertainty of 0.10 and [Fe/H], with 0.20. This can introduce new and important constraints in the age-metallicity relation for the Small Cloud, which is signicantly more complex and less studied than the one of the Large Magellanic Cloud.

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

Cette thèse a pour objectif de comprendre les différents aspects de l'évolution des amas d’étoiles massives NGC3603 et R136 qui possèdent les étoiles les plus massives connues de l'univers local. L'analyse photométrique des noyaux de R136 et NGC3603 utilisant l’imagerie infrarouge de l’instrument SPHERE sur VLT et son système d’optique adaptative extrême de SPHERE, m’a permis de détecter pour la 1ière fois un grand nombre d’étoiles de faibles masse et luminosité au coeur de ces amas et pour la plupart au voisinage des étoiles les plus lumineuses et massives. La comparaison des données de SPHERE de NGC3603 à celles du HST montre l’absence de ségrégation de masse dans le noyau de cet amas. De plus la pente de la fonction de masse de cette région est la même que celle de la région suivante et similaire aux valeurs de la MF correspondant aux régions extérieures de l’amas connues jusqu’ici. L’amas R136 est partiellement résolu par SPHERE/IRDIS dans l’IR. La majorité de ses étoiles massives ont des compagnons visuels. En prenant compte des mesures spectroscopiques et photométriques et leurs erreurs sur l'extinction et l'âge des membres de l’amas, j’ai estimé une gamme de masse pour chaque étoile identifiée. La MF a été calculée pour différents âges ainsi que les erreurs sur les masses stellaires. J’ai simulé des séries d'images de R136 grâce au code Nbody6, et les ai comparées aux observations du HST/WFPC2. Ces simulations permettent de vérifier l'effet de la binarité initiale des étoiles de l’amas, la ségrégation de masse et l'évolution des étoiles sur l'évolution dynamique propre à R136. / This thesis aims at studying 2 massive clusters NGC3603 and R136, and the mechanisms that govern their physics, These clusters host the most massive stars known in the local universe so far and are important clues to understand the formation and fate of very massive star clusters. The manuscript outlines the photometric analysis of the core of R136 and NGC3603 on the basis of HST data in the visible and the VLT high dynamic imaging that I obtained in the infrared thanks to the SPHERE focal instrument operated since 2015 and its extreme Adaptive Optics, In an extensive photometric study of these data I discovered a significantly larger number of faint low-mass stars in the core of both these clusters compared to previous works. These stars are often detected in the vicinity of known massive bright objects. By comparing HST and SPHERE measures, NGC3603 does not show any signature of mass segregation in its core since the MF slope of the very core and the next radial bin are similarly flat and agree well with the MF found in previous works of the outer regions. On the other hand R136 is partially resolved using the SPHERE/IRDIS mode with most of the massive stars having visual companions. Considering the spectroscopic and photometric errors on the extinction and the age of cluster members, I estimate a mass range for each detected star. The MF is plotted at different ages with given errors on stellar masses. Finally I demonstrate that we need more resolution to go further on studying R136 which is 7-8 times further than NGC3603.

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.