Estrutura e evolução da periferia da Grande Nuvem de Magalhães através de seus aglomerados estelares observados pelo levantamento VISCACHA

Abstract

The Large Magellanic Cloud (LMC) is the largest satellite galaxy of the Milky Way and, together with the Small Magellanic Cloud, forms the closest interacting binary galaxy system. Models of the Clouds' evolution predict that they experienced two recent close encounters: one approximately 1~2 Gyr ago and another within the last 250 Myr. Such events are expected to leave detectable signatures in their structure and star formation history. In this thesis, we present a study on the structural and evolutionary properties of the outskirts of the LMC through the analysis of 86 star clusters observed in the VISCACHA Survey. We provide the first determinations of age, metallicity, and distance for 55, 56, and 65 of them, respectively. Their characterization was performed using the SIESTA code, developed as part of the present work, to carry out a statistical comparison between the colors and magnitudes of member stars and synthetic populations generated over an isochrone grid. Among the objects studied, we discovered that the cluster SL 2 belongs to the age gap of the LMC, a period between 4~10 Gyr during which only five clusters had been previously discovered. The gap corresponds to a quiescent period in the galaxy's star formation history, which was interrupted by interactions between the Clouds. SL 2 was the first age-gap cluster discovered in the southern region of the LMC, and its mass is significantly smaller than that of other objects that are marginally younger or older than the gap period. The spatial distribution of the clusters reveals a complex structure in the outskirts of the LMC, with some regions approaching the galactic plane while others move away from it. In particular, we observe that the southwestern clusters follow the warp observed in field stars. As for the age-metallicity relation, it remains approximately homogeneous throughout the galaxy's outskirts while also being consistent with observations from more central regions. A significant exception is a metallicity dip of 0.4 dex observed in the northern region ~1 Gyr ago, which could be the result of the accretion of metal-poor material from the Small Magellanic Cloud during one of the encounters between the galaxies. In terms of star formation history, the northern region shows a larger age dispersion, while in the rest of the LMC's outskirts, the cluster ages are concentrated between 1~2 Gyr. Moreover, there is a tendency for age dispersion to decrease while its mean value increases in the east-southwest direction. Additionally, younger clusters in this region tend to be located farther from the galactic plane. Such behavior indicates that interactions between the Clouds, particularly in the last 2 Gyr, have distorted the outskirts of the LMC and promoted star formation in regions farther from its plane.