Fast radio bursts (FRBs) are millisecond-duration pulses of radio emission originating from extragalactic sources. An international team of astronomers has now detected a new FRB and localized its source to a group of two or three merging galaxies at a redshift of about 1, more than halfway back (about 8 billion years ago) to the Big Bang. Labeled FRB 20220610A, the burst is unusually bright, challenging models of the FRB emission mechanism.
This artist’s impression illustrates the path of FRB 20220610A, from a group of distant galaxies where it originated all the way to Earth, in one of the Milky Way’s spiral arms. Image credit: M. Kornmesser / ESO.
FRBs are brief pulses of radio emission originating from distant extragalactic sources.
Although the astrophysical processes that cause FRBs aren’t fully understood, the signals they produce can be used to infer information about the cosmic environments they pass through as they travel across the Universe, including the nature of their galaxies of origin and the distribution of plasma in the intergalactic medium.
Previous studies have shown that FRBs localized to host galaxies at different redshift exhibit a positive correlation between the extragalactic dispersion measure, the density of electrons the radio signal passed through as it traversed the intergalactic medium, and the host redshift — a measure known as the Macquart relation.
However, this relation has only been measured using identified FRB host galaxies at nearby redshifts.
FRB 20220610A was discovered in June 2022 by the ASKAP radio telescope in Australia.
“Using ASKAP’s array of dishes, we were able to determine precisely where the burst came from,” said Dr. Stuart Ryder, an astronomer from Macquarie University.
“Then we used ESO’s Very Large Telescope (VLT) to search for the source galaxy, finding it to be older and further away than any other FRB source found to date and likely within a small group of merging galaxies.”
The discovery confirms that FRBs can be used to measure the ‘missing’ matter between galaxies, providing a new way to ‘weigh’ the Universe.
Current methods of estimating the mass of the Universe are giving conflicting answers and challenging the standard model of cosmology.
“If we count up the amount of normal matter in the Universe — the atoms that we are all made of — we find that more than half of what should be there today is missing,” said Swinburne University of Technology’s Professor Ryan Shannon.
“We think that the missing matter is hiding in the space between galaxies, but it may just be so hot and diffuse that it’s impossible to see using normal techniques.”
“FRBs sense this ionized material. Even in space that is nearly perfectly empty they can ‘see’ all the electrons, and that allows us to measure how much stuff is between the galaxies.”
Finding distant FRBs is key to accurately measuring the Universe’s missing matter, as shown by the Australian astronomer Jean-Pierre Macquart in 2020.
“Macquart showed that the further away a fast radio burst is, the more diffuse gas it reveals between the galaxies. This is now known as the Macquart relation. Some recent fast radio bursts appeared to break this relationship,” Dr. Ryder said.
“Our measurements confirm the Macquart relation holds out to beyond half the known Universe.”
“While we still don’t know what causes these massive bursts of energy, we confirm that fast radio bursts are common events in the cosmos and that we will be able to use them to detect matter between galaxies, and better understand the structure of the Universe,” Professor Shannon said.
The team’s paper was published in the journal Science.
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S.D. Ryder et al. 2023. A luminous fast radio burst that probes the Universe at redshift 1. Science 382: 294-299; doi: 10.1126/science.adf2678
