Dark energy and cross-correlations with HIRAX 21cm intensity mapping

Observations of redshifted 21-cm emission of neutral hydrogen over a wide range of radio frequencies allow us to access redshifts that encompass a vast comoving volume, including the era of dark energy. In this talk I will present the Hydrogen Intensity Mapping and Real time Analysis experiment (HIRAX) project, which is a proposed 21cm intensity mapping experiment operating at 400-800 MHz that will measure the evolution of dark energy over the redshift range z=0.8-2.5 by using the characteristic baryonic acoustic oscillation scale as a standard ruler. The HIRAX radio telescope array will be sited in the radio-quiet Karoo astronomy reserve in South Africa and will ultimately comprise 1024 dishes, each six metres in diameter, placed in a compact configuration. I will discuss the design and project status of HIRAX and its scientific prospects. This includes dark energy forecasts as well as prospects for interesting cosmological constraints from cross-correlations of HIRAX data with other large-area cosmological surveys in the southern sky.