Characterize the intrinsic Lyman-α spectral profile at high redshift (z ≥ 7)

Characterize the intrinsic Lyman-α spectral profile emerging from galaxies at redshift z ≥ 7, explicitly accounting for the fact that asymmetric intergalactic medium transmission on the blue side of the line prevents direct reconstruction from observed spectra.

Background

In interpreting the detected Lyman-α emission from JADES-GS-z13-1-LA at z ≈ 13, the authors emphasize that the intergalactic medium (IGM) at z > 7 strongly and asymmetrically attenuates the blue side of Lyman-α. This prevents straightforward inference of the intrinsic line profile from the observed spectrum.

Although their modelling and the R1000 non-detections suggest the presence of a broad, redshifted component to enable IGM transmission, the exact emergent Lyman-α profile remains unconstrained by current data. Establishing this intrinsic profile is essential for robustly inferring systemic redshifts, outflow kinematics, ionised bubble properties, and the production and escape of ionising photons at Cosmic Dawn.