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last mo.

Astronomers Localize Fast Radio Burst at z=2.148, Setting Distance Record

Spectroscopic JWST follow-up identifies a low-mass, clumpy host galaxy that doubles the redshift reach of localized fast radio bursts

The galaxy found to be hosting FRB 2020304B. The top left image shows the field of view surrounding the observation region, with the NIRcam footprint shown on the right. The square shows the NIRSpec IFS observation footprint, and the most likely position of FRB 2020304B shown as a green cross surrounded by the localisation uncertainty (white circle). The middle images show, from left to right, the author’s NIRCam observations, Oxygen III data from NIRSpec, Hydrogen alpha data from NIRSpec, and a white light image from NIRSpec. The bottom panel shows the spectrum (black line) and its uncertainties (shaded region) of the host galaxy (Credit : South African Radio Astronomy Observatory)
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Overview

  • Follow-up JWST NIRCam and NIRSpec observations assigned FRB 20240304B a spectroscopic redshift of z = 2.148, establishing it as the most distant localized fast radio burst.
  • The host galaxy is a low-mass, clumpy system with roughly 10 million solar masses, a star-formation rate near 0.2 M☉ per year and metallicity about 10–20% of solar.
  • A dispersion measure of approximately 2,330–2,458 pc cm⁻³ and a linear polarization fraction approaching 49% extend the reach of FRBs as probes of intergalactic baryons and magnetic fields to the cosmic noon epoch.
  • Analysis of the burst’s sightline, including contributions from the Virgo Cluster and a foreground group, reveals complex magnetic-field structures across gigaparsec scales.
  • Discrepancies in media reports of the burst’s dispersion measure have highlighted the need to consult the team’s arXiv paper and data release for definitive measurements.