Cosmology

The SKA will enable pioneering cosmological surveys, probing immense volumes of the Universe which to date have been unexplored at radio wavelengths. This will be done by observing emission in both radio continuum and the 21 cm spectral line of neutral hydrogen (HI). The position in the radio sky of million of galaxies, and intensity maps made by their collective HI emission, trace the large-scale structure of the Universe, which can reveal the form and growth of dark matter structures over time. Light travelling from distant galaxies is bent by the intervening dark matter, thus creating small shape distortions (weak gravitational lensing) that can be measured to detect this otherwise invisible component. These surveys will enhance our understanding of various aspects of cosmic history, including the faint imprints of the primordial period of inflation, the early stages of galaxy formation, as well as the nature of gravity, dark energy and dark matter which determine the growth of late time large-scale structure.