The Sculptor Galaxy has an enormous halo of gas, dust and stars, which 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. “We’re very fortunate to have such a great example of a starburst galaxy in our own cosmic backyard—it’s like having a galaxy-sized laboratory on hand to conduct experiments and test our theories,” said Dr Kapinska . The study used data from the ‘GaLactic and Extragalactic All-sky MWA’, or ‘GLEAM’ survey, which was observed by the Murchison Widefield Array (MWA) radio telescope located in remote Western Australia. “With the GLEAM survey we were able, for the first time, to see this galaxy in its full glory with unprecedented sensitivity at low radio frequencies,” said Dr Kapinska.
“It’s remarkable how easily the MWA detected the diffuse halo, we managed it with just an hour of observing as the galaxy passed overhead,” she said. “We could see radio emission from electrons accelerated by supernova explosions spiralling in magnetic fields, and absorption by dense electron-ion plasma clouds —it’s absolutely fascinating.” 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. Co-author Professor Lister Staveley-Smith, from ICRAR and the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), 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.”