Prospects for clustering and lensing measurements with forthcoming intensity mapping and optical surveys

We explore the potential of using intensity mapping surveys (MeerKAT, SKA) and optical galaxy surveys (DES, LSST) to detect HI clustering and weak gravitational lensing of 21cm emission in auto- and cross-correlation. Our forecasts show that high precision measurements of the clustering and lensing signals can be made in the near future using the intensity mapping technique. Such studies can be used to test the intensity mapping method, and constrain parameters such as the HI density ${\mathrm{\Omega }}_{\mathrm{H}\mathrm{I}}$, the HI bias $b_{\mathrm{H}\mathrm{I}}$ and the galaxy-HI correlation coefficient $r_{\mathrm{H}\mathrm{I}-\mathrm{g}}$.