Intergalactic, three-dimensional map built in Western Australian outback

A survey of the night sky by the 36-dish radio telescope array in Western Australia has completed its first phase in a project that aims to build a three-dimensional intergalactic map.

The WALLABY (the Widefield ASKAP L-band All-sky Blind surveY) Pilot Survey has charted hundreds of galaxies, covering 180 square degrees of observable sky – equivalent in area to over 700 full moons.

The data, published in the Publications of the Astronomical Society of Australia, will help us better understand nearby galaxies and galactic clusters.

Data from the completed survey will help astronomers measure the distribution of dark matter, internal motion of galaxies, and how these galactic and intergalactic systems evolve and interact.

It will be the first full 3D survey of this scale. The final project will map a quarter of a million galaxies, generating 30 terabytes of data collected each eight-hour day from the ASKAP radio telescope in the remote mid-west region of Western Australia. The site provides excellent sky coverage, radio quietness and calm tropospheric conditions, making it perfect for radio astronomy.

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ASKAP is one of the precursor instruments to the Square Kilometre Array (SKA) – an international project to build the world’s largest radio telescope.

Lead author Dr Tobias Westmeier, from the University of Western Australia node of the International Centre for Radio Astronomy Research, says WALLABY’s data will allow researchers to see the universe at a scale that simply isn’t possible with optical telescopes.

“If our own Milky Way is between us and the galaxy we’re trying to observe, the sheer number of stars and dust makes it incredibly hard to see anything else,” says Westmeier. “WALLABY isn’t affected by these limitations. It’s one of the great strengths of radio surveys; they can simply peer through all the stars and dust in our own Milky Way.”

Composite image of NGC 4632 (located around 50 million light years from Earth) showing the distribution of the galaxy’s gases in a three-dimensional space. Credit: Dr Tobias Westmeier, ICRAR & Astro3D.

“WALLABY will enable us to directly map and detect hydrogen gas, the fuel for star-formation,” says co-author Dr Karen Lee-Waddell, director of the Australia SKA Regional Centre. “With this data, astronomers can accurately group galaxies to better understand how they affect each other when clustered together, providing insight on how galaxies form and change over time.”

Lee-Waddell adds that the project’s ability to show where the galaxies sit in three-dimensional space will split up those that appear clustered together but are really millions of light years apart.

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WALLABY is expected to lead to many new observations and discoveries.

“Of the over 600 galaxies measured so far, many have not been previously catalogued at any other waveband and are considered new discoveries,” says co-author Professor Lister Staveley-Smith, WALLABY’s Principal Investigator. “Over a dozen papers have been published so far describing new discoveries from these early observations.”

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