Special Physics Seminar

Illuminating the Dark Universe with Radio Observations

H. Cynthia Chiang

University of KwaZulu-Natal

Observations of redshifted 21-cm emission of neutral hydrogen are a rapidly growing area of cosmology research. Measurements across a wide range of radio frequencies allow us to access redshifts that encompass a vast comoving volume, spanning both cosmic dawn and the formation of large-scale structure. I will describe two new experiments, PRIZM and HIRAX, that aim to shed new light on the universe's evolution via redshifted 21-cm measurements. PRIZM is an experiment that is designed to study cosmic dawn by observing globally averaged 21-cm emission in a frequency range of 50-150 MHz. The instrument consists of two modified four-square antennas and a dual-polarization spectrometer back end. PRIZM deployed in April 2017 to Marion Island, an exceptionally isolated and radio-quiet location in the sub-Antarctic, and the first winter science observations are currently in progress. HIRAX is an experiment that will measure baryon acoustic oscillations (BAOs) through 21-cm intensity mapping over a frequency range of 400-800 MHz. By using the characteristic 150-Mpc BAO scale as a “ruler,” HIRAX will chart the expansion history of the universe during the period when dark energy began to dominate. HIRAX is a radio telescope array that will be sited in South Africa and will ultimately comprise 1024 dishes, each six meters in diameter, placed in a compact configuration. The construction of the first eight-element HIRAX prototype is currently near completion. I will discuss the design and project status of PRIZM and HIRAX, as well as science prospects for both experiments.