Illuminating the darkness with precision maps of neutral hydrogen across cosmic time

My proposal is to map out the 3D structure of the Universe over an unprecedentedly broad swath of cosmic time, covering 13 billion years of cosmic history. I will do this by using radio telescopes to detect the 21cm emission from neutral hydrogen.

The detailed statistical properties of the maps will allow us to answer some of the most pressing questions in cosmology, such as how fast space is expanding, what the physical properties of dark energy are, and how the first stars and galaxies lit up the Universe.All experiments currently trying to make these observations are severely limited by systematic effects, exacerbated by the extremely high dynamic range between the cosmological signal and many other sources of radio emission.

Even tiny calibration errors can cause huge artefacts in the data that make it extremely difficult to pick out the target signal.

While a great deal of work has gone into designing methods to analyse the data, they are not yet accurate enough by a factor of 100 by some measures.I will develop a statistical analysis framework called Total Calibration that can deliver the remaining two orders of magnitude of improvement, and apply it to the most sensitive data available.

The result will be precise, systematics-free maps and the most robust statistical measurements of large-scale structure ever made in the radio.

Total Calibration seeks to model all of the relevant degrees of freedom in the data simultaneously, in one large global model of the signal, contaminants, and the calibration of the telescope.

This is highly complex, and has never been done before.By applying total calibration to sensitive but complex data from two cutting-edge telescopes, HERA and MeerKAT, I will obtain the most robust constraints on the 21cm signal to date, from redshifts 01.4 (late times) and 527 (reionisation/Cosmic Dawn), to constrain the physical processes that shaped the cosmic energy budget at high redshift and any possible evolution of dark energy.