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Astrophysics

Subaru meets JWST: A Direct Measurement of Ly Escape Fraction at with Dual Narrow-Band Imaging

Shunta Shimizu, Nobunari Kashikawa

Featured July 13, 2026

Original Paper

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Simply

Scientists used two powerful telescopes, JWST and Subaru, to directly measure how much Ly\alpha light escapes from distant galaxies, finding that more light escapes from compact, less dusty ones during the early universe.

In depth
The paper presents a novel approach to directly measure the Ly\alpha escape fraction at during the Epoch of Reionization by combining JWST/NIRCam F470N and Subaru/HSC NB872 imaging. This unique dual narrow-band technique allows for simultaneous observation of H and Ly fluxes from the same galaxies, providing a more robust, model-independent quantification of how much Ly light escapes early galaxies.

Key Takeaways

  • 1
    A direct measurement of the Ly\alpha escape fraction at is achieved using a unique dual narrow-band imaging technique with JWST and Subaru telescopes.
  • 2
    The median Ly escape fraction is found to be , consistent with an increase towards higher redshifts, and shows no significant dependence on H\alpha luminosity within the probed range.
  • 3
    Individual galaxy analysis reveals that Ly escape positively correlates with Ly\alpha equivalent width and negatively correlates with the UV continuum slope and rest-frame UV size, suggesting regulation by compact, low-attenuation star-forming regions.

Conceptual Flow

HIGH LEVEL
1
Methodology: How was it done?

The study used two special camera filters on different telescopes to see two specific types of light from the same distant galaxies at the same time.

Distant Galaxy Light
Filter Specific Colors
H-alpha Light
Lyman-alpha Light
2
Results: What did they find?

They found that a small but significant amount of Lyman-alpha light escapes these early galaxies, especially from their bright, compact parts, which helps us understand how the universe became transparent.

Galaxy Brightness
Galaxy Size
Light Colors
Connect Traits to Escape
Escape Fraction Insights