Webb Pinpoints Host of Farthest Fast Radio Burst Yet
Webb confirmed the host galaxy of FRB 20240304B at redshift 2.148, a small dwarf galaxy, suggesting a young magnetar origin.
The story in focus
Astronomers using the James Webb Space Telescope identified the host galaxy of the most distant fast radio burst yet seen, FRB 20240304B, at redshift 2.148. The unexpectedly small dwarf galaxy suggests the burst likely came from a young magnetar rather than a neutron star merger, according to a study in Science.
- MeerKAT detected FRB 20240304B on March 4, 2024
- Webb measured the host galaxy's redshift at 2.148
- The host is 1,000 times less massive than expected
A record distance
The MeerTRAP team detected the millisecond radio flash with the MeerKAT telescope and designated it FRB 20240304B. The radio data suggested an extreme distance, but ground-based telescopes could not see a galaxy at the burst's location, so the team turned to Webb.
Webb's NIRCam instrument detected the host galaxy, and NIRSpec measured its redshift at 2.148, placing it 3 billion years after the big bang. Most fast radio bursts found so far occurred billions of years later in cosmic history.
An unexpected dwarf galaxy
Most FRB host galaxies are massive and star-forming. This one was 1,000 times less massive than the team expected, though it was actively forming stars during cosmic noon, when star formation peaked. The study was published in Science, with Manisha Caleb of the University of Sydney as lead author.
The team argues the result makes a neutron star merger unlikely, because such mergers take billions of years. A young magnetar left behind by a supernova could produce a burst sooner, matching the young host.
Tracing cosmic structure
The burst's signal carried imprints of matter along its path, including a previously unknown galaxy cluster at redshift 0.3 and the nearby Virgo Cluster. The team estimates MeerKAT may detect several bursts per year beyond redshift 1.0, with Webb needed to characterize their hosts.
Why does the host galaxy's age matter for explaining fast radio bursts?
A small, young, star-forming galaxy fits a magnetar born in a recent supernova. Neutron star mergers take billions of years, so they would be expected in older galaxies with evolved stellar populations.
Sources & further reading
- Webb Measures Distance to Farthest Fast Radio Burst, Suggesting Origin - NASA Science ↗science.nasa.gov
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