New radio telescope to probe dark energy and mysterious radio flashes

August 22nd, 2018, Published in Articles: EngineerIT

South Africa has launched a multimillion-Rand global project in radio astronomy that will conduct ground-breaking science in astrophysics while building on existing excellence in the country. The Hydrogen Intensity and Real Time Analysis eXperiment (HIRAX) telescope will be located at the Square Kilometre Array (SKA) South Africa site in the Karoo.

The HIRAX telescope project is jointly funded by the University of KwaZulu-Natal (UKZN) and the Department of Science and Technology (DST) through the National Research Foundation (NRF). HIRAX will be a compact 400 – 800 MHz radio telescope array of 1024 six-metre dishes that will map about a third of the sky during its four years of observation. It has two primary science goals: to constrain dark energy and measure structure at high redshift, and to study radio transients and pulsars. The project was conceptualised in 2014 and submitted to the National Research Foundation for funded by the NRF Institutional Engagement Programme Directorate.

Fig. 1: Artist impression of the 1024 dishes in to be constructed at the SKA site [UKZN].

Speaking at the launch in Durban, Science and Technology Minister Mmamoloko Kubayi-Ngubane said that HIRAX will enhance the national system of innovation by building research and innovation capabilities in the country. “The project will help South Africa develop innovative solutions, particularly in instrumentation and big data processing, directly impacting other economic sectors through technology transfer”.

HIRAX will observe unresolved sources of neutral hydrogen via their redshifted 21 cm emission line (“hydrogen intensity mapping”). It is generally acknowledged that the study of the emission line from neutral hydrogen may be astronomers’ main hope to study the formation of the first structures during the dark ages and the Epoch of Reionisation. The resulting maps of large-scale structure at redshifts 0,8 – 2,5 will be used to measure baryon acoustic oscillations (BAO). BAO are a preferential length scale in the matter distribution that can be used to characterise the expansion history of the universe and thus understand the properties of dark energy.

HIRAX will improve upon current BAO measurements from galaxy surveys by observing a larger cosmological volume (larger in both survey area and redshift range) and by measuring BAO at higher redshift when the expansion of the universe transitioned to dark energy domination. HIRAX will complement CHIME, a hydrogen intensity mapping experiment in the Northern Hemisphere, by completing the sky coverage in the same redshift range.

HIRAX’s location in the Southern Hemisphere also allows a variety of cross-correlation measurements with large-scale structure surveys at many wavelengths.

Daily maps of a few thousand square degrees of the Southern Hemisphere, encompassing much of the Milky Way galaxy, will also open new opportunities for discovering and monitoring radio transients.

The HIRAX correlator will have the ability to rapidly and efficiently detect transient events. This new data will shed light on the poorly understood nature of fast radio bursts (FRBs), enable pulsar monitoring to enhance long-wavelength gravitational wave searches, and provide a rich data set for new radio transient phenomena searches.

Transient events are events which change rapidly, unleashing typically vast amounts of energy events such as gamma ray bursts or supernovae. Typically, these events are only visible for short periods of time, sometimes in multiple wavelengths across the electromagnetic spectrum.

The experiment will be managed by UKZN and is a result of a large global collaboration with at least eight South African institutions, and another dozen internationally. The researchers will undertake a technical programme that involves building the instrument, carrying out science observations and analysing the raw data.

UKZN vice-chancellor and principal, Dr Albert van Jaarsveld, said “UKZN is very proud of its HIRAX team, which has made a significant impact at a national and international level in terms of the importance and significance of the HIRAX telescope project and its synergies with the SKA initiative. The project is led from UKZN by a dynamic young team of astronomers that are breaking new ground and leveraging the SKA investment to grow a new generation of young astronomers in KZN and South Africa.”

HIRAX will be able to determine the characteristics of dark energy during a critical period in our universe, between 7- and 11-billion years ago when dark energy became the dominant component in the universe causing it to expand at an accelerated rate.

The main HIRAX array, combined with small arrays in partnering African countries, will be able to localise mysterious radio flashes called fast radio bursts (FRB) within their host galaxies, a feat never achieved before. This will be a vital first step in determining the cause of these bursts.

The HIRAX principal investigator, UKZN’s Professor Kavilan Moodley, said “The HIRAX project is exciting because we are working with a dynamic group of students and scientists that work on all aspects of the project, from building the telescope and analysing the data to scientific interpretation. We are aiming to use our competitive advantage of being on the excellent SKA SA Karoo site to have an impact on the study of dark energy and fast radio bursts.”