The Science
Some for everyone
The Big Bang and today's Universe of stars and galaxies are both well studied — but far less is known about the time in between, roughly 0.35–1 billion years after the Big Bang, when the cosmos went from a cooling fog of neutral gas to the realm of objects we see today.
As it expanded and cooled, electrons and protons combined into the first neutral atoms — mostly hydrogen. Gravity pulled that gas together until fusion ignited the first stars and galaxies (the Cosmic Dawn), which then re-ionised the surrounding hydrogen during the Epoch of Re-ionization.
We study these epochs by observing radio signals naturally emitted by hydrogen — inferring the first stars from their imprint on the surrounding gas, much as one reads a landscape from the shadows in the fog covering it.
For the keen astronomer
The first luminous sources formed after cosmic recombination (the CMB, ~378,000 yr after the Big Bang, z ≈ 1100) and before the galaxy-filled Universe of today. Their radiation heated and re-ionised the neutral hydrogen pervading the primordial cosmos.
Neutral hydrogen has a rest wavelength of 21 cm; observing at low radio frequencies lets us study its redshifted emission and absorption from those early gas clouds — one of the prime probes of the Dark Ages, Cosmic Dawn and EoR.
The future SKA will do full tomography of this signal, while a stand-alone radiometer can target the sky-averaged (global) monopole across cosmic time — the approach behind REACH.
How we observe
REACH ↗
Our radiometer in the Karoo, South Africa, targeting the global 21-cm signal from the Cosmic Dawn.
CosmoCube ↗
A space mission to study the Universe's Dark Ages from the far side of the Moon's orbit.
HERA ↗
Detecting the complementary 21-cm power spectrum at smaller spatial scales.
LOFAR & SKA ↗
Interferometers we contribute to — from LOFAR surveys to the SKA and its Science Data Processor.
Methods
Techniques we develop, with applications across and beyond radio cosmology.
›Data analysis for 21-cm cosmology — Bayesian inference with nested sampling, physics-rooted models, maximally smooth functions.
›Calibration of radiometers.
›Signal extraction from noise, with applications in astronomy and EM metrology.
›Fast, accurate calibration of wideband, ultra-large phased arrays.
›Accurate modelling and compact representation of phased-array beams affected by electromagnetic mutual coupling.
Technology
Supported by our labs at the Cavendish, the MRAO and Cambridge's HPC facilities — building electromagnetic technology for a better society, inspired by radio astronomy.
›Development of the SKA Science Data Processor.
›Digital research infrastructure for the SKA UK Science Regional Centre.
›Design and development of antennas and low-noise receivers for radio astronomy (e.g. SKALA4 for SKA1-LOW, the HERA front-end), higher-frequency systems such as the SKA MFAA phased array, and the SKA AAVS1 prototype station.
›Measurement techniques for EM metrology of very large structures using UAVs, and ultra-sensitive EM sensors for the IoT society.
›Technology for ultra-fast digital communications (e.g. surface-wave launchers).