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Distant galaxy identified as the origin of mysterious bright burst

Media release

For the first time an international team of scientists, using a combination of radio and optical telescopes including the Murchison Widefield Array (MWA), has managed to identify the precise location of a fast radio burst (FRB).

-- CSIRO’s Parkes radio telescope, which detected FRB150418, superimposed on an image showing the distribution of gas in our Milky Way galaxy. An artist’s impression of a single fast radio burst is shown above the dish. Credit: Swinburne Astronomy Productions

FRBs are bright radio flashes which generally last for only a few milliseconds and are very difficult to detect. Only 16 others had been observed before this discovery, and how and where they originated from was completely unknown.

Curtin University researcher Dr Ramesh Bhat, of the Department of Physics and Astronomy, said that FRBs showed a frequency-dependent dispersion, which was a delay in the radio signal caused by how much matter it had gone through.

“With this specific FRB we were able to not only measure the distance it had travelled, but also the density, allowing us to weigh the matter in the Universe as the burst travels to us,” Dr Bhat said.

The discovery was published in the journal Nature today and confirms the standard cosmological model of the composition of the Universe.

The study was conceived under ‘The Dynamic Universe’ research theme of the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), of which many of the authors at Curtin and other Australian universities are a part.

Dr Evan Keane, lead author and project scientist for the Square Kilometre Array (SKA) Organisation, said this was the first time a fast radio burst had been used to conduct a cosmological measurement.

“In the past, FRBs have been found by sifting through data months or even years later. By that time it is too late to pinpoint the origin of the burst,” Dr Keane said.

To remedy this, researchers developed their own observing system to detect FRBs within seconds and to immediately alert other telescopes when there is still time to search for more evidence after the flash.

The specific burst studied was detected on 18 April last year by the CSIRO’s 64m Parkes radio telescope in New South Wales – the same instrument that had found 14 of the 16 other known FRBs.

Within hours of the FRB hitting the Parkes dish, Swinburne PhD student Shivani Bhandari pointed the Australia Telescope Compact Array’s six 22m dishes in the direction of the burst and monitored the region over the next few weeks.

The researchers detected a radio afterglow that lasted for around six days before fading away, and by combining these observations with those of an optical telescope in Hawaii, they were able to identify an elliptical galaxy some six billion light years away as the location of the burst.

“It’s the first time we’ve been able to identify the host galaxy of an FRB,” Dr Keane said.

The optical observation also provided researchers with the redshift – the speed at which the galaxy is moving away from us due to the accelerated expansion of the Universe – and subsequently the first distance to an FRB.

This was the first time that an instrument – the MWA – was ‘shadowing’ Parkes at the precise time that a fast radio burst went off, and it obtained radio data from the exact same region at a lower frequency than Parkes operates.

“The MWA sees 100 times more sky than Parkes, but the burst was not detected at the MWA’s long wavelengths. This allowed us to constrain the spectral nature of its emission, thinning the list of plausible scenarios that might produce FRBs,” Dr Bhat said.

Looking forward, the SKA, with its extreme sensitivity, resolution and wide field of view is expected to be able to detect and locate hundreds of FRBs and pinpoint their host galaxies. A much larger sample will enable precision measurements of cosmological parameters such as the distribution of matter in the Universe and provide a refined understanding of dark energy.

Notes to Editor

CAASTRO is a collaboration between Curtin University, The University of Western Australia, the University of Sydney, the Australian National University, the University of Melbourne, Swinburne University of Technology and the University of Queensland. It is funded under the Australian Research Council Centre of Excellence program and receives additional funding from the seven participating universities and the NSW State Government Science Leveraging Fund.

Curtin University is a joint venture partner with The University of Western Australia in The International Centre for Radio Astronomy Research (ICRAR) which receives support and funding from the State Government of Western Australia.