Research project Bubbles in the early universe – charting the history of reionization

The most recent of these transitions is known as cosmic reionization, during which the overwhelming majority of intergalactic matter (mostly hydrogen gas) was transformed from a cool, neutral state to a warm, ionized medium.  There is little doubt that this process was driven by ultraviolet radiation emitted by the first stars and black hole-related phenomena in proto-galactic structures.  However, charting the progress of reionization with time, as well as empirically deriving the actual fraction of neutral material, are both extremely challenging.

This VR-funded project aims make new measurements of the neutral fraction of the universe, when it was below 10 per cent of its current age. We will employ a new method that measures ultraviolet radiation from galaxies, using spectroscopic data obtained from an ongoing Large Program (128 hours) with the Very Large Telescope at the European Southern Observatory in Chile. We will use comparative ‘calibration’ data obtained at later times to infer the physical size of ionized regions, and both the fraction of neutral gas and the volume filled by bubbles.