ANU and CSIRO astronomers witness the lights going out on nearby dwarf galaxy

Glynis Quinlan 12 November 2018

A radio image of hydrogen gas in the Small Magellanic Cloud captured by the CSIRO’s powerful ASKAP telescope. Image credit: Naomi McClure-Griffiths et al, CSIRO’s ASKAP telescope.

Astronomers from the Australian National University and the CSIRO have witnessed the slow death of a neighbouring dwarf galaxy, which is gradually losing its power to form stars.

Thanks to the CSIRO’s powerful Australian Square Kilometre Array Pathfinder (ASKAP), the astronomers have witnessed this death in the finest detail ever possible.

A new peer-reviewed study published in Nature Astronomy uses images of the dwarf galaxy, which is known as the Small Magellanic Cloud and is a tiny fraction of the size and mass of the Milky Way galaxy.

Lead researcher Professor Naomi McClure-Griffiths from the ANU said the features of the radio images were more than three times finer than previous Small Magellanic Cloud images, allowing her team to probe the interactions between the small galaxy and its environment with more accuracy.

“We were able to observe a powerful outflow of hydrogen gas from the Small Magellanic Cloud,” said Professor McClure-Griffiths, who is from the Research School of Astronomy and Astrophysics at ANU.

Another radio image of the Small Magellanic Cloud. Image credit: Naomi McClure-Griffiths et al, CSIRO’s ASKAP telescope.

“The implication is the galaxy may eventually stop being able to form new stars if it loses all of its gas,” she said.

“Galaxies that stop forming stars gradually fade away into oblivion. It’s sort of a slow death for a galaxy if it loses all of its gas.”

Professor McClure-Griffiths said the discovery, which is part of a project that investigates the evolution of galaxies, provided the first clear observational measurement of the amount of mass lost from a dwarf galaxy.

“The result is also important because it provides a possible source of gas for the enormous Magellanic Stream that encircles the Milky Way,” she said.

“Ultimately, the Small Magellanic Cloud is likely to eventually be gobbled up by our Milky Way.”

CSIRO co-researcher Dr David McConnell said the ASKAP telescope was unrivalled in the world for this kind of research due to its unique radio receivers that give it a panoramic view of the sky.

CSIRO’s ASKAP radio telescope. Image credit: CSIRO.

“The telescope covered the entire SMC galaxy in a single shot and photographed its hydrogen gas with unprecedented detail,” he said.

Hydrogen is the most abundant element in the universe, and is the main ingredient of stars.

“ASKAP will go on to make state-of-the-art pictures of hydrogen gas in our own Milky Way and the Magellanic Clouds, providing a full understanding of how this dwarf system is merging with our own galaxy and what this teaches us about the evolution of other galaxies,” Dr McConnell said.

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