"Global-assembly has pursued an analysis of chemical abundances in the GC systems, as well as in the metal-poor field stars observed in the Galactic Halo and in the Bulge. This project has resulted in 27 peer-reviewed papers, a successful proposal, with me as Principal Investigator, and several other proposals where I am co-Investigator.
As a major result, I have provided a first chemical atlas of the stellar populations observed along the GC chromosome maps. Despite the high level of heterogeneity, my work has introduced a ""Universal chromosome map"", represented in Figure 1, which highlights the common properties in the multiple population phenomenon in different GCs. Specifically: 1) two main peaks in the star density can be identified at the same location on the Universal map, one corresponding to the first population and the other to the second population; 2) the separation among these main populations occurs at the same level of the map in all GCs; 3) the first population in typically elongated suggesting a chemical inhomogeneity.
I have investigated two of the most intriguing and critical aspects revealed by the maps, namely the presence of two main morphologies of ""chromosome maps"", Type-I (the most common in the Milky Way) and Type-II maps, and the apparent lack of chemical homogeneity among stars that were commonly associated with a single stellar population, the first population stars. My work has demonstrated that all the Type-II GCs have internal variations in the heavy elements including iron, which is unusual for relatively-low mass stellar systems like GCs. Surprisingly, I have demonstrated that the elongation on the map observed in the first population is associated with internal variations in the overall metallicity. The challenge is now to understand how these variations originated in the first hundreds million years of the history of our Universe. To understand this issue I have been awarded of telescope time at the Very Large Telescope of the European Southern Observatory.
Going to the external galaxies, the analysis of GCs younger than typical Milky Way GCs has revealed that these objects, similarly to old GCs, display internal variations in He, although the level of enhancement is small. This result suggests that the typical chemical variations associated with the classical multiple populations phenomenon are not confined to a formation in the high redshift Universe.
A new line of research of this project has been the investigation of the kinematics of individual populations in GCs. By exploiting data from the Gaia satellite different populations have resulted to display various degrees of kinematic anysotropy, and one GC has been found with hints of different rotation in its two stellar populations.
I have co-supervised the work of one bachelor and one master thesis student (E. Ventura, E. Dondoglio), and I am currently supervising two PhD students (G. Cordoni, E. Dondoglio).
For the dissemination activities I have presented my work at the MODEST conference organized by the International Astronomical Union (May, 2019, Bologna - Italy), where I have given an invited talk; I have organized a workshop at the European Week of Astronomy (
https://eas.unige.ch/EWASS2019/session.jsp?id=SS23(si apre in una nuova finestra)) and I have been invited to give a seminar at the University of Sharjah (UAE).
As part of the outreach and public engagement activities I have participated the European Researchers’ Night, and I have given lectures of basic astronomy in primary schools for science week."
