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Unconstrained Lyα and N V emission affecting interpretation of the Lyα break

Ascertain the strengths of Lyα and N V λ1240 emission in the z=14.44 galaxy MoM-z14 using higher-resolution, higher-SNR spectroscopy to enable robust modeling of the Lyα break and its implications for the intergalactic medium neutral fraction and any potential damped Lyα absorption.

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Background

The authors model the sharp Lyman-α break of MoM-z14 and find it consistent with z≈14.42; the break shape may hint at a partially ionized IGM and a lack of a strong damping wing. However, the current NIRSpec/prism data lack the spectral resolution and SNR needed to quantify possible Lyα and N V emission.

Without firm constraints on Lyα and N V, detailed interpretation of the damping wing and the ionization state of the surrounding IGM remains uncertain. Improved measurements of these lines are necessary to test scenarios such as an ionized bubble around MoM-z14 or significant neutral gas in its vicinity.

References

However, we end this section by emphasizing caution that at the moment we are unable to constrain the strength of Ly$\alpha$ or #2{N}{V} emission, which at this low resolution and SNR makes detailed interpretation of the break challenging.

— A Cosmic Miracle: A Remarkably Luminous Galaxy at $z_{\rm{spec}}=14.44$ Confirmed with JWST (2505.11263 - Naidu et al., 16 May 2025) in Subsection “An Absent Damping Wing at z_spec=14.44?” (Section Results; §3.4)