Radio detections of the redshifted 21cm line with neutral hydrogen (HI) intensity mapping surveys can provide a new way to probe the evolving history of the Universe and tackle fundamental cosmological questions. Intensity mapping (IM) measures the fluctuations of the HI signal tracing the underlying matter distribution, and therefore can be used to reconstruct the matter power spectrum without the need to detect individual galaxies. This means that intensity mapping surveys can observe large volumes very fast, and give us access to large cosmological scales while providing excellent redshift information.
We explore the possibility of performing such a survey with the South African MeerKAT radio telescope, which is a precursor to the Square Kilometre Array (SKA). We are also proposing to use cross-correlations between the MeerKAT intensity mapping survey and optical galaxy surveys, in order to mitigate important systematic effects and produce robust cosmological measurements. Our forecasts show that precise measurements of the
clustering and lensing signals can be made in the near future. These can be used to constrain HI and cosmological parameters across a wide range of redshift.