Australasian Science: Australia's authority on science since 1938

Astronomers Probe Halo of Starburst Galaxy

Astronomers have used a radio telescope in outback Western Australia to see the halo of a nearby starburst galaxy in unprecedented detail.

A starburst galaxy is a galaxy experiencing a period of intense star formation. This one, known as the Sculptor Galaxy (NGC 253), is approximately 11.5 million light-years from Earth. It has an enormous halo of gas, dust and stars that had not been observed before at frequencies below 300 MHz. The halo originates from galactic “fountains” caused by star formation in the disk and a super-wind coming from the galaxy’s core.

“The Sculptor Galaxy is currently forming stars at a rate of five solar masses each year, which is a many times faster than our own Milky Way,” said lead researcher Dr Anna Kapinska of The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR).

The study used data from the “GaLactic and Extragalactic All-sky MWA” (GLEAM) survey, which was observed by the Murchison Widefield Array (MWA) radio telescope in remote Western Australia. The MWA is a precursor to the Square Kilometre Array (SKA) radio telescope, part of which will be built in Western Australia in the next decade.

“It’s remarkable how easily the MWA detected the diffuse halo,” Kapinska said. “We managed it with just an hour of observing as the galaxy passed overhead. We could see radio emission from electrons accelerated by supernova explosions spiralling in magnetic fields, and absorption by dense electron-ion plasma clouds.”

Co-author Prof Lister Staveley-Smith of ICRAR and the ARC Centre of Excellence for All-sky Astrophysics said the SKA will be the largest radio telescope in the world and will be capable of discovering many new star-forming galaxies when it comes online. “But before we’re ready to conduct a large-scale survey of star-forming and starburst galaxies with the SKA we need to know as much as possible about these galaxies and what triggers their extreme rate of star formation,” he said.

“By getting to the bottom of what’s causing this galaxy to produce so many stars, we can better understand how other galaxies form, grow and change over time throughout the universe.”