Multiple Populations among very low mass stars in 47 Tucanae

Globular clusters (GCs) are stellar clusters tightly bound by gravity. They are some of the oldest objects in the Universe. Recent studies of their color-magnitude diagrams revealed that almost all GCs host multiple stellar populations marked by different chemical compositions. There are two conflicting scenarios that try to explain the formation of multiple populations: single-generation and multiple-generation. In this thesis, I analyze the Hubble Space Telescope data of Tucanae 47. While the previous works are based on the most-massive GC stars, I explore the lower main sequence. Indeed, the properties of very low-mass (VLM) stars provide constraints on the formation scenarios and shine light on the assembly of the Galactic halo. I analyzed multi-band images of distinct fields with different radial distances from the cluster center. Hence, I derived high-precision photometry in optical and infrared bands, and identified the main stellar populations of 47 Tucanae among VLM stars. I constrained the chemical composition of the distinct stellar populations and compared it with the results obtained for more-massive GC stars. Moreover, I determined, for the first time, the radial distribution of the multiple populations of VLM stars. Finally, I used the results to disentangle the formation scenarios of the multiple populations.