Existence of favorable ionizing-photon escape sightlines during reionization

Determine whether favorable sightlines that permit ionizing-photon escape from massive, high-column-density galaxies exist during the Epoch of Reionization.

Background

The paper discusses whether massive, luminous galaxies can contribute substantially to the ionizing-photon budget. Although lower-redshift Lyman-continuum emitters demonstrate that ionizing photons can escape through ionized channels in otherwise opaque neutral media, it remains unresolved whether comparable sightlines existed during the Epoch of Reionization, when the intergalactic medium was predominantly neutral. This uncertainty bears directly on whether massive galaxies could have been important sources of reionization.

References

However, it is unclear whether such favorable sightlines exist during the EoR, and even if these sightlines did exist, the radiation must cross a foreground IGM that is predominantly neutral.

— Discovery of the Lyman-$α$ Forest in a Star-Forming Galaxy at $z \approx 7.57$: Implications for the Timing and Topology of Cosmic Reionization  (2609.38080 - Helton et al., 29 Sep 2026) in Section 1, Introduction