UNIMASS · Galaxy evolution through Cosmic Time

Final Activity Report Summary - UNIMASS (Galaxy Evolution through Cosmic Time)

Galaxies are the beacons that light up the distant regions of the Universe. Understanding galaxies is essential for undertaking precision cosmology. Yet, their formation is still a mysterious process, especially the formation and evolution of their stellar component. With this project we have significantly enhanced our understanding of how galaxies evolve. This objective was achieved by means of a synergetic study that brought together the most fundamental approaches to the problem. This synergetic method was the key novelty of this Excellence Grant and - after experience we believe is the most successful one. First, we developed sophisticated galaxy evolution models - so called stellar population models - as tools for studying galaxies. These models - available through a dedicated website - are meant to be useful to the worldwide astrophysical community. For example, the models became a standard tool for the Sloan Digital Sky Survey collaboration, a 50-million-dollars international experiment based in the United States aimed at unveiling the equation of state of the Universe by studying millions of galaxies. The models are already in use at several research institutes all over the world. This is a great result for the European astrophysical research. In parallel to the model development, we analysed real galaxy data, from observatories all over the world, with the aim at unveiling the processes behind galaxy evolution in an empirical fashion. This research granted us with excellent new results that have been published in specialised journals and are being already highly cited in the astrophysical community. As a brief summary, we have shown that the light emission from galaxies in the late-time Universe is contributed to by ancient stars with a low chemical composition, opposite to the widespread view suggesting newly formed stars in these galaxies. For young galaxies in the primeval Universe, we obtained the new result that the formation of stars in these galaxies appears to proceed with an exponentially-increasing mode, and we published a model which mimics this process. Independent confirmation of this result came from other research groups. Furthermore, we are publishing an article that explains in details the advantages and the limits of galaxy data analysis. In particular, we studied the dependence of the success of data analysis on the wavelength range adopted in observations. This methodology article will be precious for maximising the success of observational campaigns, with effect on the economics around telescope time assignment. Selective results have been already used by colleagues working at the NASA Spitzer Space Telescope. In parallel to the analysis of galaxy data, we worked with theoretical galaxy models. In particular, we assessed - for the first time - the impact of stellar ingredients on theoretical galaxy formation simulations. This aspect was a completely original topic of this grant. The results of this research - published in four international publications - are revolutionary. We could show that the comparison between data and simulations, on which our knowledge of the galaxy evolution process is based, is completely dominated by the stellar ingredient in the models, especially at distant cosmic epochs. The correction of this effect allowed us to perform a compelling comparison between simulations and observations and to identify the epochs at which models and data diverge mostly, which will serve as basis for future work. The Team has employed seven researchers - one with over 10 year experience as Team Leader, two experienced researchers and four early-stage researchers, over four years with excellent balance of gender and nationality. Three PhD titles will be granted this year and six out of seven researchers found excellent positions in academia, the seventh willing to continue his career outside research as a teacher.

Data: CORDIS, © European Union