PRIN 2022: PROGETTI DI RICERCA DI RILEVANZA NAZIONALE - Prot. 2022MMEB9W - CUP C53D23001200006

Abstract

Globular clusters (GCs) are the remnants of the most compact star formation "explosions" we know of and have always been among the most intensively studied stellar systems. Yet, we have never really understood why it was so easy to produce such massive and extremely dense stellar aggregates, in such a widespread fashion and especially so in the early Universe. Moreover, with the discovery that they harbor multiple stellar populations (MP) answering these questions became harder than ever before. The most recent discoveries about the MP properties dictate a major effort to understand the phenomenon. The objective of this project is to shed light on the formation mechanisms of GCs and understand the origin of their MPs. This will represent a major step forward to constrain a wide variety of closely related issues, such as star formation mechanisms and initial mass functions in dense early environments, stellar evolution and nucleosynthesis, the role of proto-GCs in the cosmic reionzation and their contribution to the assembly of the Milky Way Halo. We propose to explore all these issues with a synergic plan coordinating our observational and a theoretical efforts. For the observational approach we will take advantage of a variety of techniques that we have developed and fully master, namely spectroscopy and precision photometry, pushing up to their limits the present-day biggest telescopes on the Earth and in space. The enormous amount of observational data from the Hubble Space Telescope and the 10m-class telescopes on the Earth that we have gathered will be analyzed to get a detailed chemical inventory of the complex intertwining of the multitude of stellar populations observed in GCs. The project will include the analysis of new spectroscopic and photometric data that the James Webb Space Telescope will observe as part of our approved programme (Cycle 1, GO2560; PI: Marino). This exquisite dataset will allow us to provide a full characterization of all the observed stellar populations in GCs down to the very low mass stars in the M-dwarfs' regime. Thus, we plan to answer questions such as: how MPs formed at high-z? What is the nature of stars producing materials with such compositions? Do GCs formed inside dwarf galaxies that later dissolved? In particular, to answer this last question we plan to exploit early released data from the James Webb Space Telescope that will allow us to directly "see" GCs in formation in the very distant Universe. In parallel, stellar evolutionary models and their nucleosynthesis products will be calculated to help identifying the nature of the polluting stars. A complete synergy between these coordinated approaches is a fundamental aspect of this project that aims at strengthening a leading team in Italy including the major observational and theoretical experts dedicated to solve the puzzle of GC formation.