Early on, the Universe consisted of a near-uniform mixture of hydrogen, helium, dark matter and radiation. The emergence of structure from a stochastic background of fluctuations in the period between 400,000 years and 1 billion years after the Big Bang is the main subject of this proposal. This transition from the "dark ages" in the history of the Universe to "cosmic dawn" saw the formation of the first autonomous sources of radiation, stars and black holes. This "renaissance" of light led to the heating and reionization of the intergalactic medium. The first supernova explosions start the process of metal and dust enrichment, releasing in their surroundings elements heavier than helium and dust grains condensed in their expanding ejecta. Despite the amount of new data rapidly accumulating on the primeval Universe, the transition from the dark ages to cosmic dawn and the physical properties of the sources responsible for the reionization of the intergalactic medium still remain largely unconstrained.
Our research aims to address the following three key questions:
(i) What is the nature of the first stars to shine through the Universe?
(ii) What is the best observational strategy to observe the first stars?
(iii) What was the contribution of the first stars to cosmic reionization?
In the last years we developed a unique combination of theoretical models exploring the Universe at cosmic dawn with semi-analytical models and cosmological hydro-dynamical simulations. We constantly upgrade our models by improving their physics, to make them ready for the next fresh data provided by new surveys planned with new observational facilities, such as the James Webb Space Telescope and the European Extremely Large Telescope. The funding requested by our team will principally allow the acquisition of small computational facilities, the support of exchange activities with external collaborators, and payment of publication fees.
