The gradual decline of Lyα visibility in the CANDELS fields: evidence for the combined effects of galaxy evolution and reionization

@misc{napolitano2026gradual,
  title = {{The gradual decline of Ly$α$ visibility in the CANDELS fields: evidence for the combined effects of galaxy evolution and reionization}},
  author = {L. Napolitano and L. Pentericci and A. Ferrara and M. Llerena and M. Dickinson and A. Calabrò and S. L. Finkelstein and R. Begley and P. Arrabal Haro and A. Arroyo-Polonio and B. E. Backhaus and D. Bevacqua and A. Bhagwat and M. Bischetti and M. Castellano and S. -J. Chang and E. R. Cueto and V. D'Odorico and C. T. Donnan and M. Galbiati and G. Gandolfi and M. Giavalisco and M. Hirschmann and J. Kartaltepe and A. M. Koekemoer and K. K. Knudsen and R. A. Lucas and S. Mascia and L. Paquereau and B. Pérez-D\'ıaz and C. Piscitelli and R. Rana and P. Santini and A. J. Taylor and E. Taylor and R. Tripodi and S. M. Wilkins and L. Y. A. Yung},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.00199},
  eprint = {2609.00199},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.00199},
}

TY  - UNPB
TI  - The gradual decline of Lyα visibility in the CANDELS fields: evidence for the combined effects of galaxy evolution and reionization
AU  - L. Napolitano
AU  - L. Pentericci
AU  - A. Ferrara
AU  - M. Llerena
AU  - M. Dickinson
AU  - A. Calabrò
AU  - S. L. Finkelstein
AU  - R. Begley
AU  - P. Arrabal Haro
AU  - A. Arroyo-Polonio
AU  - B. E. Backhaus
AU  - D. Bevacqua
AU  - A. Bhagwat
AU  - M. Bischetti
AU  - M. Castellano
AU  - S. -J. Chang
AU  - E. R. Cueto
AU  - V. D'Odorico
AU  - C. T. Donnan
AU  - M. Galbiati
AU  - G. Gandolfi
AU  - M. Giavalisco
AU  - M. Hirschmann
AU  - J. Kartaltepe
AU  - A. M. Koekemoer
AU  - K. K. Knudsen
AU  - R. A. Lucas
AU  - S. Mascia
AU  - L. Paquereau
AU  - B. Pérez-D\'ıaz
AU  - C. Piscitelli
AU  - R. Rana
AU  - P. Santini
AU  - A. J. Taylor
AU  - E. Taylor
AU  - R. Tripodi
AU  - S. M. Wilkins
AU  - L. Y. A. Yung
PY  - 2026
DA  - 2026/09/01
PB  - arXiv
DO  - 10.48550/arxiv.2609.00199
UR  - https://arxiv.org/abs/2609.00199
AB  - We investigate the evolution of Lyα visibility and the physical properties of Lyα emitters (LAEs) across the five CANDELS fields using publicly available JWST/NIRSpec PRISM spectroscopy. Our catalog comprises 3446 spectroscopically confirmed sources at 4 $\leq $ z < 14.2, including 3361 star-forming galaxies (SFGs), of which 539 are robust (S/N > 3) LAEs. We measure the fraction of LAEs with EW_0 > 25A (X_Lyα) and trace its redshift evolution in two UV luminosity bins, namely -20.25 < M_UV < -18.75 and -21.75 < M_UV < -20.25. Within the fainter-UV range, X_Lyα increases from z = 5 to z = 6 at 3σ significance and subsequently declines toward higher redshifts with a significant monotonic trend at z > 6. We also investigate the physical properties of both LAEs and the full SFG population. We find that the stellar mass, UV slope β, stellar reddening, SFR, metallicity, sSFR, and burstiness of LAEs remain approximately stable with redshift. The only exception is the mass-weighted age which decreases with increased redshift. Conversely, the properties of the full SFG population evolve significantly, progressively approaching the region of galaxy-property space occupied by LAEs as redshift increases. This suggests that galaxy evolution may enhance the intrinsic production and escape of Lyα photons toward earlier epochs. We argue that this effect should be accounted when inferring the evolution of the neutral hydrogen content of the IGM from the observed visibility of Lyα emission. To this end, we employ a physically motivated framework based on the Attenuation-Free Model, jointly accounting for galaxy evolution and IGM attenuation. Our observations favor reionization histories that proceed gradually over scenarios characterized by a rapid increase in the cosmic neutral hydrogen fraction.
ER  -