BINGO!

Understanding galaxy formation is one of the major goals of modern cosmology. While observers primarily use large galaxy surveys for mapping structure and galaxy evolution nearby and far-away, spectacular measurements of the cosmic microwave background have allowed the understanding of the initial conditions that seeded the cosmic structures we see today. Models predict that the dark matter seeded by primordial quantum fluctuations formed the architecture of the Universe, a 'cosmic web' of sheets and filaments of dark and normal (baryonic) matter. We now know the basic constituents of mass-energy today: 73% dark energy, 23% dark matter, 1% baryons in galaxies, and 3% ''hidden' baryons. The next challenge is to understand the physical processes of the formation of galaxies and structures and their interactions with the tenuous medium in between galaxies: the Intergalactic Medium (IGM). The IGM traces the cosmic web of matter in the Universe, including normal ('baryonic') matter and the mysterious dark matter known to pervade the Universe. The IGM forms and connects galaxies, fuels them throughout time, and may be profoundly changed by their feedback of energy, matter, and chemical elements. Tremendous progress has been made over the last decade in establishing a broad cosmological framework in which galaxies and large-scale structure develop hierarchically over time, as a result of gravitational instability of material dominated by dark matter. However, many questions remain: how do galaxies form and how are they related to their environments? When did the first luminous objects form and what was their nature? All of these questions are closely related to the amount of baryons and metals contained in the Universe at any given time, and in particular in the Intergalactic Medium (IGM). Once formed, galaxies interact with the IGM by pervading it with ionising photons, by polluting it with heavy elements formed in stars and supernovae, and by driving supersonic, galactic winds into intergalactic space. The feedback processes of photo-ionisation (and photo-heating), chemical enrichment, and shock-heating of the IGM by the first stars and galaxies is thought to have profound consequences for the formation of subsequent generations of galaxies. We propose here to study the intergalactic medium, its baryonic content and interactions with galaxies using a mix of observational techniques, state-of-the-art simulations and dedicated instrumentation.