Our research focuses on two broad themes – Observational Cosmology and Relativistic Astrophysics.

Relativistic Astrophysics

Our theory group applies the theory of General Relativity to the study of compact objects, such as white dwarfs, neutron stars, and black holes. We also investigate alternative gravity theories and theoretical cosmology.

Academic staff:  Gareth Amery, Rituparno Goswami, Gabriel Govender, Kesh Govinder, Sudan Hansraj, Sunil Maharaj (SARChI Chair in Gravitating Systems), Subharthi Ray

Observational Cosmology

Our observational cosmologists study the large scale structure of the universe; the formation and evolution of galaxies; search for signatures from the formation of the first stars; and attempt to uncover the nature of dark matter and dark energy, using millimetre and radio wavelength observations. We describe some of our ongoing projects below.

Cosmic Microwave Background Experiments

The cosmic microwave background (CMB) is the oldest light in the universe – coming to us from approximately 400,000 years after the Big Bang. Measurements of CMB anisotropies – temperature fluctuations at the micro-kelvin level – tell us that we live in a universe dominated by dark matter and dark energy; only 5% of the energy density of the universe is in the form of ordinary matter. ACRU researchers are involved in several CMB experiments, such as the Atacama Cosmology Telescope, the Planck mission, SPIDER, and Simons Observatory.   The latest generation of experiments are pursuing measurements of the polarisation of the CMB – with the goal of detecting evidence for gravitational waves from inflation in the very early universe. The C-Band All Sky Survey (C-BASS), in which UKZN is involved, will help in this work by providing measurements of Galactic foreground emission.

Academic staff: H. Cynthia Chiang (honorary staff), Matt Hilton, Yin-Zhe Ma, Kavilan Moodley, Jon Sievers (honorary staff)

Galaxy Clusters

Galaxy clusters are the most massive gravitationally collapsed objects in the Universe. Their rate of growth over cosmic time depends upon the amount of dark matter and dark energy in the Universe. Clusters host hot gas atmospheres that can be detected using X-ray and Sunyaev-Zel’dovich (SZ) effect observations, and from these signatures we can infer their masses. Studies of clusters also tell us about the effect of environment on galaxy evolution, and the effects of star formation and active galactic nuclei in these galaxies on the surrounding intracluster gas. ACRU researchers are investigating all aspects of cluster evolution – from radio to X-ray wavelengths – using clusters detected by the Atacama Cosmology Telescope project, the Planck mission, and the XMM Cluster Survey.

Academic staff: Matt Hilton, Yin-Zhe Ma, Kavilan Moodley, Jon Sievers (honorary staff)

Large Scale Structure

Observations of the large scale structure of the Universe provide another way to measure cosmological parameters, and investigate the nature of the mysterious dark energy.  At ACRU we are pioneering efforts to measure the large scale structure by neutral hydrogen (HI) intensity mapping, with experiments such as the Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX), led by UKZN. We are also involved in the Baryon acoustic oscillations from Integrated Neutral Gas Observations (BINGO) experiment, and efforts to make similar measurements with FAST – the world’s largest single-dish telescope, located in China. As well as mapping the distribution of neutral hydrogen in the Universe, these experiments will also detect many Fast Radio Bursts – mysterious flashes in the radio sky, the cause of which is currently unknown.

Academic staff: H. Cynthia Chiang (honorary staff), Matt Hilton, Yin-Zhe Ma, Kavilan Moodley, Jon Sievers (honorary staff)

The Epoch of Reionization

Most of the hydrogen gas in the Universe today is ionised, a process that began with the birth of the first stars during the Epoch of Reionisation. We expect to see the signature of the first stars “switching on”  at FM radio frequencies – but this requires finding a site far from terrestrial signals (such as radio stations). ACRU researchers are leading an effort to detect this signal from Marion Island – approximately 2000 km southeast of Cape Town, on the way to Antarctica – using the PRIZM (Probing Radio Intensity at high-Z from Marion) telescope.

Academic staff: H. Cynthia Chiang (honorary staff), Jon Sievers (honorary staff)