“ESTUDO DE AGLOMERADOS ABERTOS NA PONTE MAGALHÃES”

Abstract

Star clusters are fundamental tools for studying the formation and evolution of galaxies. In particular, those located in tidal structures of the Magellanic Clouds such as the Magellanic Bridge, a structure of gas and stars connecting the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) provide valuable clues about the history, dynamics, and chemical evolution of these regions.

This dissertation aims to analyze the astrophysical and structural properties of the clusters NGC 456, NGC 460, and NGC 465, located at the easternmost end of the Magellanic Bridge, using photometric data from the VISCACHA catalog, complemented by information from the Gaia space mission. To achieve this, photometric decontamination techniques were applied, comparing the cluster region with surrounding field areas, which made it possible to identify a reliable sample of probable members.

With this sample, isochrone fitting was performed on the color–magnitude diagrams (CMDs) in order to derive physical parameters such as age, distance, extinction, and metallicity. In addition, structural parameters were estimated by fitting King profiles to the stellar radial density profiles.

Our results indicate that the analyzed clusters have ages between 4 and 6 million years, exhibit relatively high metallicities ([Fe/H] ~ –0.4 dex) compared to typical SMC values ([Fe/H] ~ –0.9 dex), and are located at heliocentric distances of around 58 kpc. The presence of dust and gas, along with the absence of evolved stars in the CMDs, reinforces the young nature of these systems.

Taken together, their spatial and physical properties suggest a common origin, possibly from the same giant molecular cloud in the vicinity of NGC 465. This cluster likely occupied a privileged position within the cloud, forming first with the richest stellar population. This allowed it to develop a long-lived, centrally condensed structure, unlike NGC 456 and NGC 460, which may not survive the gas expulsion process and could dissolve over the next few million years.

In the context of the Magellanic Bridge, this study shows that it is an active star-forming region, likely fed by material stripped from the central body of the Small Magellanic Cloud during its most recent interaction with the Large Magellanic Cloud.