Constraining reionization-era Lyα escape with JELS-MUSE: a highly complete Hα-selected sample at z∼6.1

Abstract

The Lyα escape fraction, f_esc^Lyα, probes both the interstellar medium (ISM) conditions governing ionizing photon escape and the rising neutral fraction of the IGM through the Epoch of Reionization (EoR). Characterising the intrinsic, ISM-driven distribution of f_esc^Lyα before IGM attenuation becomes dominant is essential to interpret the observed decline in Lyα visibility through the EoR. We present f_esc^Lyα measurements for a highly complete, Hα-flux-limited sample of 24 star-forming galaxies at z ≈ 6.1, drawn from the JWST Emission Line Survey (JELS) and observed in Lyα with VLT/MUSE as part of the JELS-MUSE Large Area Survey. We detect Lyα in 12 of 24 sources and a Lyα emitter fraction of X_Lyα = 33 ± 12 per cent using the canonical EW(Lyα) > 25 mathringA definition. Incorporating non-detections via reverse Kaplan-Meier survival analysis yields ⟨ f_esc^Lyα ⟩ = 0.07^+0.04_−0.03, consistent with an independent stacked-flux estimate of 0.08^+0.02_−0.02. Using reionization simulations matched to the area, depth, and redshift range of our survey, we find that all galaxies are expected to experience broadly similar IGM transmission, so we postulate that the large scatter in f_esc^Lyα reflects genuine ISM-driven variance rather than differences in the surrounding IGM. Among the detections, higher f_esc^Lyα galaxies tend to have lower nebular dust attenuation, bluer UV slopes, and lower stellar mass, consistent with feedback-regulated escape through localised, low-column-density ISM channels around star-forming regions. These results benchmark intrinsic Lyα escape at the end of reionization, against which IGM suppression at z > 7 can be interpreted.

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BibTeX RIS

BibTeX

@misc{patrick2026constraining,
  title = {{Constraining reionization-era Ly$α$ escape with JELS-MUSE: a highly complete H$α$-selected sample at $z\sim6.1$}},
  author = {A. L. Patrick and K. J. Duncan and Z. Li and C. A. Pirie and A. M. Swinbank and L. C. Keating and S. R. Flury and R. Begley and P. N. Best and M. Brinch and A. C. Carnall and F. Cullen and J. S. Dunlop and E. Ibar and J. Matthee and D. J. McLeod and A. Puglisi and H. M. O. Stephenson and J. P. Stott},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.02558},
  eprint = {2609.02558},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.02558},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Constraining reionization-era Lyα escape with JELS-MUSE: a highly complete Hα-selected sample at z∼6.1
AU  - A. L. Patrick
AU  - K. J. Duncan
AU  - Z. Li
AU  - C. A. Pirie
AU  - A. M. Swinbank
AU  - L. C. Keating
AU  - S. R. Flury
AU  - R. Begley
AU  - P. N. Best
AU  - M. Brinch
AU  - A. C. Carnall
AU  - F. Cullen
AU  - J. S. Dunlop
AU  - E. Ibar
AU  - J. Matthee
AU  - D. J. McLeod
AU  - A. Puglisi
AU  - H. M. O. Stephenson
AU  - J. P. Stott
PY  - 2026
DA  - 2026/09/02
PB  - arXiv
DO  - 10.48550/arxiv.2609.02558
UR  - https://arxiv.org/abs/2609.02558
AB  - The Lyα escape fraction, f_esc^Lyα, probes both the interstellar medium (ISM) conditions governing ionizing photon escape and the rising neutral fraction of the IGM through the Epoch of Reionization (EoR). Characterising the intrinsic, ISM-driven distribution of f_esc^Lyα before IGM attenuation becomes dominant is essential to interpret the observed decline in Lyα visibility through the EoR. We present f_esc^Lyα measurements for a highly complete, Hα-flux-limited sample of 24 star-forming galaxies at z ≈ 6.1, drawn from the JWST Emission Line Survey (JELS) and observed in Lyα with VLT/MUSE as part of the JELS-MUSE Large Area Survey. We detect Lyα in 12 of 24 sources and a Lyα emitter fraction of X_Lyα = 33 ± 12 per cent using the canonical EW(Lyα) > 25 mathringA definition. Incorporating non-detections via reverse Kaplan-Meier survival analysis yields ⟨ f_esc^Lyα ⟩ = 0.07^+0.04_−0.03, consistent with an independent stacked-flux estimate of 0.08^+0.02_−0.02. Using reionization simulations matched to the area, depth, and redshift range of our survey, we find that all galaxies are expected to experience broadly similar IGM transmission, so we postulate that the large scatter in f_esc^Lyα reflects genuine ISM-driven variance rather than differences in the surrounding IGM. Among the detections, higher f_esc^Lyα galaxies tend to have lower nebular dust attenuation, bluer UV slopes, and lower stellar mass, consistent with feedback-regulated escape through localised, low-column-density ISM channels around star-forming regions. These results benchmark intrinsic Lyα escape at the end of reionization, against which IGM suppression at z > 7 can be interpreted.
ER  -

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