Assembly history of the Magellanic Bridge and Small Magellanic Cloud Wing from star clusters

• Autor(a) principal: Oliveira, Raphael Augusto Pereira de
• Data de Publicação: 2023
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/14/14131/tde-26052023-113849/
• topic: galáxias: aglomerados: geral; galáxias: evolução; galaxies: evolution; galaxies: star clusters: general; Magellanic Clouds; Nuvens de Magalhães

The stellar clusters located in the Magellanic System are very important in the determination of the star formation history and chemodynamical evolution of the Small and Large Magellanic Clouds (SMC and LMC). The Magellanic Bridge is the structure formed by tidal forces and ram pressure during a recent collision between the LMC and SMC, the pair of satellite galaxies closest to the Milky Way. The analysis of the ages and chemical signatures of its stellar population is crucial to distinguish which is the most adequate model to explain the origin and evolution of the Magellanic Clouds-Milky Way system. There are currently two competing scenarios: (i) the Magellanic Clouds were independent satellites and got bound recently, at ~2 Gyr ago; (ii) the Magellanic System is old and on its first passage across the Milky Way in the last ~2 Gyr. In this context, the importance of the Bridge stellar clusters has been neglected in the literature. Its formation scenario during a collision some 200-300 million years ago, as proposed by the models, would imply kinematic signatures, as well as age and metallicity gradients along its extension, which still need to be observationally confirmed. To elucidate this question, this work combined deep photometric data of the VISCACHA and SMASH surveys, homogeneously deriving age, metallicity, distance, structural parameters and mass of 33 Wing/Bridge clusters, by means of robust and modern tools such as Markov chain Monte Carlo and machine learning. Two groups were identified among the 33 clusters: 13 well-studied clusters older than the Bridge, with ages between 0.5 and 4.7 billion years and [Fe/H] < -0.6; and 15 clusters younger than 200 million years and with [Fe/H] > -0.5, probably formed in the Bridge itself. The main results include: (i) the ages and metallicities were derived for the first time for 9 and 18 clusters, respectively; (ii) two metallicity dips were detected in the Bridge age-metallicity relation, with ages similar to the formation of the Magellanic Bridge and Stream; (iii) a stellar mass of 3-5×10^5 Msun was estimated for the Bridge, more than one order of magnitude higher than previous estimates; (iv) the Bridge clusters are young and metal-rich, with [Fe/H] ~ -0.4. The study also involved the analysis of clusters in other SMC regions and the use of spectroscopic data to refine the results.