The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a radio telescope array that will map nearly all of the southern sky in radio continuum and neutral hydrogen line emission over a frequency range of 400 to 800 MHz. The primary goal of HIRAX is to use 21-cm intensity mapping to measure baryon acoustic oscillations (BAOs): these are remnant ripples in the distribution of galaxies that are imprinted by primordial sound waves that existed in the early universe. The characteristic BAO length scale can be used as a “ruler” for charting the expansion history of the universe and for shedding light on the nature of dark energy. HIRAX science goals include the following:
- Probe dark energy via 21-cm intensity mapping
- Search for radio transients and pulsars
- Study neutral hydrogen absorbers
- Measure diffuse polarization of the Galaxy
- Cross-correlations with other southern surveys, e.g. LSST
- SKA technology demonstrator
HIRAX will be an interferometer that comprises roughly 1000 six-meter dishes placed in a close-packed, redundant configuration, and the tentative deployment location will the be the SKA site in the Karoo desert, South Africa. The operating frequency of 400-800 MHz corresponds to a redshift range of 0.8 to 2.5. The dishes will be stationary and will have a 5-10 degree field of view, and the dishes will be periodically repointed in elevation in order to build up coverage of the southern sky. HIRAX is highly complementary to the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and will share much of the back-end technology, including FPGA-based ICE boards and the GPU correlator.
The HIRAX project was given preliminary approval by the South African National Research Foundation in 2015. The first prototype dish testing has begun, and an initial eight-element array is scheduled for construction and deployment in 2016.
The HIRAX project gratefully acknowledges funding support from the following sources: