WALLABY surveys two-thirds of the sky for hydrogen

ASTRO 3D astronomers have begun using CSIRO’s $188 million Australian Square Kilometre Array Pathfinder (ASKAP) in a major science survey project – WALLABY (Widefield ASKAP L-band Legacy All-sky Blind surveY) – in the first step in observing 75% of the sky, sampling approximately 500 000 galaxies.


The project, led by Dr Baerbel Koribalski from CSIRO and Dr Lister Staveley-Smith from the The University of Western Australia, has begun processing mind-boggling huge amounts of data to look for neutral hydrogen gas (HI). The data will be sifted through by astronomers with the help of supercomputers at the Pawsey Centre in Perth, Western Australia.

Neutral hydrogen is individual hydrogen atoms, comprised of a proton and an electron. It is the most common form of normal matter in the universe and the building block of stars and galaxies. In the nearby Universe, most of the HI is found in galaxies. Astronomers map HI which actually maps galaxies. This produces much more information about galaxies and their formation than just visible light alone.


The WALLABY team have spent the second half of 2017 reducing data from four 30 sq. degree fields (the angular area viewed by the telescope), and have started producing images of individual galaxies.

The images here show the HI in one beam (out of 36) after combining seven nights of ASKAP data. They found two gas-rich dwarf galaxies in the vicinity of a nearby spiral galaxy (IC 5201).

Credit: Dane Kleiner (CASS)

The collage shows IC 5201 on the top row – the optical image (left), the HI distribution (middle) and the HI velocity field – which shows how fast the gas is moving (right). The bottom row shows the same thing for the two dwarf galaxies.

This research will help scientists better understand the interplay between hydrogen gas and the processes that lead to star formation in galaxies, and therefore how they form and evolve.