AsianScientist (Mar. 1, 2016) – Using radio and optical telescopes, an international team of scientists have identified the distant location of a fast radio burst (FRB) for the first time. This discovery is significant, as it confirms the current cosmological model of the distribution of matter in the universe as we know it. Their work was published in Nature.
FRBs are mysterious, bright radio flashes which generally last only a few milliseconds. Their cause is still unknown, and they could potentially be associated with a long list of phenomena. FRBs are very difficult to detect; before this discovery, only 16 had been observed so far.
“In the past, FRBs have been found by sifting through data months or even years later. By that time, it is too late to do follow up observations,” said lead author Dr. Evan Keane at the Square Kilometre Array Organisation (SKAO) in Australia.
To solve this, the team developed its own observation system at Swinburne University of Technology in Australia to detect FRBs within seconds, and to immediately alert other telescopes while there is still time to search for more evidence in the aftermath of the initial flash.
The fast radio burst in question was detected on April 18 last year by the Commonwealth Scientific and Industrial Research Organisation’s (CSIRO) 64-meter Parkes radio telescope. An alert immediately went out to telescopes around the world to follow up with their observations.
Within a few hours, CSIRO’s Australian Telescope Compact Array (ATCA), as well as international facilities, were looking for the signal. Their observations revealed a radio afterglow that lasted for around six days before fading away.
This afterglow enabled astronomers to pinpoint the location of the FRB about a thousand times more precisely than for previous observed events.
Research team members from the University of Tokyo (UTokyo), the National Astronomical Observatory of Japan (NAOJ), and Konan University next examined an optical image of the FRB taken a day after the first flash by the NAOJ’s 8.2-meter Subaru Telescope in Hawaii. The image revealed a possible source: an elliptical galaxy some six billion light-years away.
Follow-up spectroscopic observations yielded a redshift measurement for the source, which allowed astronomers to calculate its distance. Redshift indicates the speed at which the galaxy is moving away from us, due to the expansion of the universe.
“For the first time, we have identified the host galaxy and measured the distance to a fast radio burst,” said Dr. Tomonori Totani, professor at UTokyo’s Department of Astronomy, who led the optical observation effort.
Furthermore, FRBs exhibit a frequency-dependent dispersion, a delay in the radio signal caused by how much material it has gone through.
“Until now, the dispersion measure is all we had. By also having a distance, we can now measure how dense the material is between the point of origin and Earth, and compare that with the current model of the distribution of matter in the universe,” explained Dr. Simon Johnston, of CSIRO’s Astronomy and Space Science division.
“Essentially, this lets us ‘weigh’ the universe, or at least the normal matter it contains.”
In the current model, the universe is believed to be made of 70 percent dark energy, 25 percent dark matter and five percent ‘ordinary’ matter, the matter that makes up everything we see. However, through observations of stars, galaxies and hydrogen, astronomers have only been able to account for about half of the ordinary matter; the rest cannot be seen directly and so has been referred to as ‘missing.’
“The good news is, our observations and the model match. We have found the missing matter,” explained Keane.
“It’s the first time a fast radio burst has been used to conduct a cosmological measurement.”
Nevertheless, the origin of FRBs still remains a mystery. It is hoped that future observations of FRBs in a variety of wavebands reveal more details about this enigmatic astronomical phenomenon.
The article can be found at: Keane et al. (2016) The Host Galaxy of a Fast Radio Burst.
———
Source: Subaru Telescope; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.
