FLAGS: First Light and galaxy Assembly 

Early on, the Universe consisted of a near-uniform mixture of hydrogen, helium, dark matter and radiation. The emergence of structures 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. The transition from the ‘dark ages’ in the history of the Universe to ‘cosmic dawn’ saw the formation of the first stars and galaxies. This ‘renaissance’ of light led to the 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 nature of the first stars and galaxies and their role in cosmic reionization still remain largely unconstrained. Excitingly, we are at the verge of a revolution in this field as the successful launch of the James Webb Space Telescope (JWST) will enable an unprecedented epochal leap forward in our understanding of the transition from the dark ages to cosmic dawn. 

The proposed FLAGS team is optimally placed to contribute to this extraordinary adventure, by leveraging our unique theoretical expertise in the modelling of low-metallicity star formation and early metal and dust enrichment, as well as our participation to the first JWST surveys that will target the high-z Universe.

The FLAGS project  is aimed at:

(i) characterising the properties of stellar populations in the first galaxies detected by JWST at 6 < z < 10, with a special focus on their stellar mass distribution, star formation rate, age, star formation history and ionising photon emissivity;

(ii) identifying, among JWST targets, low metallicity galaxies all the way to Pop III stellar populations, i.e. the first generations of stars born out of pristine, metal free gas;

(iii) quantifying the dust content in the interstellar medium of JWST targets and the fraction of dust-obscured star formation;

(iv) provide a framework for interpreting JWST data aimed at studying the onset of star formation in the Universe and the history of star formation, chemical enrichment and reionization in the first Gyr.

This ambitious scientific program is complemented by a thorough dissemination plan. In the spirit of our previous experiences, we are committed to a prompt release of data, tools and theoretical simulations. We have also designed a lively outreach plan to present our scientific results, anticipating the impact that early JWST observations will have on the general public. The FLAGS team is made of internationally acknowledged leaders in the field, well balanced between theory and observations, and geographically concentrated to ensure maximum efficiency and effectiveness. Our track records in the last years demonstrates that we are capable of meeting our ambitious goals.