The infrared image on the left shows the field of view of the Parkes radio telescope with the area where the signal came from marked in cyan. On the right are successive zoom-ins on that area. At the bottom right is the Subaru optical image of the FRB galaxy, with the superimposed elliptical regions showing the location of the fading 6-day afterglow seen with ATCA. Credit: © D. Kaplan (UWM), E. F. Keane (SKAO)
An international research team including Max Planck Institute for Radio Astronomy in Bonn, Germany used a radio and optical telescopes to identify the precise location of a fast radio burst (FRB) in a distant galaxy, allowing them to conduct a unique census of the Universe’s matter content.They confirmed current cosmological models of the distribution of matter in the Universe.
On April 18, 2015, a FRB was detected by Parkes radio telescope of CSIRO in Australia within the framework of the SUrvey for Pulsars and Extragalactic Radio Bursts (SUPERB) project. An international alert was triggered to follow it up with other telescopes and within a few hours, telescopes around the world were looking for the signal, including CSIRO’s ATCA and the Effelsberg Radio Telescope in Germany.
FRBs are mysterious bright radio flashes generally lasting only a few milliseconds, origin unknown. FRBs are very difficult to detect; before this discovery only 16 had been detected. Thanks to the ATCA’s six 22-m dishes and their combined resolution, the team was able to pinpoint the location of the signal with much greater accuracy than has been possible in the past and detected a radio afterglow that lasted for around 6 days before fading away. It enabled them to pinpoint the location of the FRB ~1000X more precisely than previously.
![This image shows the increased delay in the arrival time of the Fast Radio Burst as a function of the frequency. The delay in the signal is caused by the material it goes through between its point of origin in a distance of 6 billion light years and Earth. [less] © E. F. Keane (SKAO)](https://www.mpifr-bonn.mpg.de/3547309/standard_sans_both.jpg)
This image shows the increased delay in the arrival time of the Fast Radio Burst as a function of the frequency. The delay in the signal is caused by the material it goes through between its point of origin in a distance of 6 billion light years and Earth. [less] © E. F. Keane (SKAO)
For understanding the physics of such events it is important to know basic properties like the exact position, the distance of the source and whether it will be repeated. “Our analysis leads us to conclude that this new radio burst is not a repeater, but resulting from a cataclysmic event in that distant galaxy,” states Michael Kramer, MPIfR. MPIfR’s Effelsberg Radio Telescope was also used for radio follow up.
FRBs show 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” explains Simon Johnston, CSIRO. “..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% dark energy, 25% dark matter and 5% ‘ordinary’ matter, the matter that makes 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 could not 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” explains Evan Keane. “It’s the first time a fast radio burst has been used to conduct a cosmological measurement.”
Looking forward, the Square Kilometre Array, SKA, with its extreme sensitivity, resolution and wide field of view is expected to be able to detect many more FRBs and to 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.
The SUrvey for Pulsars and Extragalactic Radio Bursts (SUPERB) is a large-scale astrophysics project using several telescopes, high-speed GPU analysis codes, a large supercomputer and artificial neural networks to identify new astrophysical discoveries. In particular it deals with pulsars, and explosions in space known as Fast Radio Bursts (FRBs). http://www.mpifr-bonn.mpg.de/pressreleases/2016/4
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