Adrian Liu’s research is focused on making the largest ever three-dimensional map of our Universe.
This can be done by mapping the distribution of neutral hydrogen atoms, since it is ubiquitous in space and conveniently emits faint radio waves. Therefore, observations with large radio telescopes enable the construction of such a map.
Studying maps of hydrogen can reveal enormous insights into the behaviour of our Universe, just as studying a street map might reveal the underlying dynamics of a city. For example, the distribution of highways and the clustering patterns of skyscrapers might provide information about how commuters flow downtown during the morning rush hour. In this case, maps provide the only direct view of our own Cosmic Dawn, when matter condensed into first-generation stars and galaxies.
Liu is part of the Hydrogen Epoch of Reionization Array (HERA) collaboration, which aims to provide the first precision observational constraints on Cosmic Dawn. HERA’s design is comprised of 350 radio dishes, each 14 meters in diameter, located in the South African Karoo desert. It is one of the largest and most sensitive low-frequency radio telescopes ever constructed, allowing researchers to fulfill the immense promise of cosmological hydrogen mapping.
Kern, N.S., A. Liu, A.R. Parsons, A. Mesinger and B. Greig. "Emulating Simulations of Cosmic Dawn for 21cm Power Spectrum Constraints on Cosmology, Reionization, and X-ray Heating." Astrophysics Journal, 848, 23 (2017).
Schutz, K. and A. Liu. "Pulsar timing can constrain primordial black holes in the LIGO mass window." Physical Review D, 95, 023002 (2016).
Liu, A., Y. Zhang and A.R. Parsons. "Spherical Harmonic Analyses of Intensity Mapping Power Spectra." Astrophysics Journal, 833 (2016): 242.
Liu, A., J.R. Pritchard, Allison et al. "Eliminating the optical depth nuisance from the CMB with 21 cm cosmology." Phys. Rev. D 93, 043013 (2016).
Liu, A., A.R. Parsons and C.M. Trott. "The Epoch of Reionization Window: I. Mathematical Formalism." Phys. Rev. D 90, 023018 (2014).