Testing Gravity with MeerKAT and the SKA

Abstract

The new 64-dish radio telescope array MeerKAT will be absorbed into the international Square Kilometre Array (SKA) in late 2020s. These two telescope arrays will produce three-dimensional maps of the integrated intensity of the 21cm emission from neutral hydrogen in galaxies, out to redshifts of 1:5 and 3 respectively. These maps contain a signature of the growth of large-scale structure in the Universe. This signature can be uncovered via redshift space distortions of the two-point correlation function, or power spectrum, of the 21cm brightness temperature uctuations. The growth rate governs the amplitude of the anisotropic signal from redshift-space distortions. It is a powerful probe of gravity and its measurement has the potential to test whether general relativity holds. We use models of the 21cm intensity and its power spectrum, starting from a simple linear model of redshift-space distortions and then extending to nonlinear models. With these models, we make Fisher forecast predictions of the precision with which MeerKAT and the SKA can measure the growth rate