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Astrophysics

Investigating the magnetic field in the inter-cluster filament between Abell 3667 and Abell 3651 with POSSUM

C. Stuardi, S. P. O'Sullivan

Featured September 7, 2026

Original Paper

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Simply

By carefully removing our galaxy's magnetic "fog" from radio signals, scientists used a powerful new telescope survey to measure the weak magnetic fields in a distant cosmic bridge connecting two galaxy clusters, finding them to be surprisingly strong.

In depth
The study pioneers the direct measurement of magnetic fields in an individual cosmic filament by leveraging the POSSUM radio survey's dense data. They developed a sophisticated Galactic foreground subtraction method to isolate the faint extragalactic signal, then applied Bayesian modeling with two simplified magnetic field scenarios to constrain the field strength in the filament.

Key Takeaways

  • 1
    The paper presents the first direct magnetic field constraints in an individual X-ray-detected inter-cluster filament, finding strengths of .
  • 2
    A novel annulus method was employed to accurately subtract the highly structured Galactic foreground Rotation Measure, which is critical for detecting weak extragalactic signals.
  • 3
    The study highlights the critical importance of precise Galactic foreground modeling for future extragalactic magnetism studies with next-generation radio telescopes.

Conceptual Flow

HIGH LEVEL
1
Methodology: How was it done?

Scientists used radio signals from distant objects, carefully removed the magnetic interference from our own galaxy, and then used the remaining signal to figure out the magnetic field in a huge cosmic bridge.

Distant Radio Signals
Our Galaxy's Magnetic Fog
Remove Interference
Cosmic Bridge Magnetic Field
2
Results: What did they find?

They found that the cosmic bridge has magnetic fields, which are stronger than expected for such a vast, empty space, suggesting active processes are at play.

Cosmic Bridge
Weak Magnetic Fields (Expected)
New Measurement
Stronger Magnetic Fields (Found)

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