---
OA_place: publisher
OA_type: diamond
PlanS_conform: '1'
_id: '23050'
abstract:
- lang: eng
  text: The resonant scattering nature of Lyα photons interacting with neutral hydrogen
    makes Lyα emitters (LAEs) robust tracers of the intergalactic neutral hydrogen
    fraction, and thus sensitive probes of cosmic reionization. We present an extensive
    study of the Lyα evolution from galaxies at 4.5 ≤ z ≤ 11 in the UDS field, observed
    as part of the CAPERS survey, and complemented with spectra from the DAWN JWST
    Archive. The combined sample includes 651 spectroscopically confirmed Lyα-break
    galaxies, among which we find 73 S/N > 3 LAEs in JWST-NIRSpec PRISM spectra. We
    trace the redshift evolution of the LAE fraction with EW0 > 25 Å (XLyα) between
    z = 5 and z = 9, extending such an analysis to the UDS field for the first time.
    At z = 5 and 6, the UDS results agree with the average JWST XLyα values from multiple
    fields. However, JWST measurements are consistently lower than ground-based results.
    To investigate this, we compare JWST observations to a population of star-forming
    galaxies at z ∼ 6 observed with VLT-FORS2. We find that a Lyα slit-loss of 35
    ± 10% in JWST spectra accounts for the offset, as the resonant Lyα emission is
    more spatially extended than the stellar continuum. From z = 6 to 7, the UDS field
    shows a significant drop in Lyα visibility, from which we infer a neutral hydrogen
    fraction of XHI = 0.7–0.9. Finally, we identify two robust ionized bubbles at
    z = 7.29 and 7.77, with radii of Rion = 0.6 and 0.5 physical Mpc and photometric
    overdensities of N/⟨N⟩ = 3 and 4, based on candidate counts down to the photometric
    completeness limit. Compared to the large ionized region at z ∼ 7 in the EGS field,
    these results indicate significant field-to-field variation, supporting a patchy,
    inhomogeneous reionization process.
acknowledgement: 'We thank the anonymous referee for the constructive feedback provided.
  LN acknowledges support from grant “Progetti per Avvio alla Ricerca – Tipo 1, Unveiling
  Cosmic Dawn: Galaxy Evolution with CAPERS” (AR1241906F947685) and from PRIN 2022
  MUR project 2022CB3PJ3 – First Light And Galaxy aSsembly (FLAGS) funded by the European
  Union – Next Generation EU. LN, LP, AB, and BC acknowledge support from the ERC
  synergy grant 101166930 – RECAP. This work is based on observations made with the
  NASA/ESA/CSA James Webb Space Telescope, obtained at the Space Telescope Science
  Institute, which is operated by the Association of Universities for Research in
  Astronomy, Incorporated, under NASA contract NAS5-03127. These observations are
  associated with programs #6368, #4233, #1215, #2565, and #3543. Support for program
  number GO-6368 was provided through a grant from the STScI under NASA contract NAS5-03127.
  The data were obtained from the Mikulski Archive for Space Telescopes (MAST) at
  the Space Telescope Science Institute. These observations can be accessed via DOI.
  Some of the data products presented in this work were retrieved from the Dawn JWST
  Archive (DJA). DJA is an initiative of the Cosmic Dawn Center (DAWN), which is funded
  by the Danish National Research Foundation under grant DNRF140.'
article_number: A102
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: L.
  full_name: Napolitano, L.
  last_name: Napolitano
- first_name: L.
  full_name: Pentericci, L.
  last_name: Pentericci
- first_name: M.
  full_name: Dickinson, M.
  last_name: Dickinson
- first_name: P.
  full_name: Arrabal Haro, P.
  last_name: Arrabal Haro
- first_name: A. J.
  full_name: Taylor, A. J.
  last_name: Taylor
- first_name: A.
  full_name: Calabrò, A.
  last_name: Calabrò
- first_name: A.
  full_name: Bhagwat, A.
  last_name: Bhagwat
- first_name: P.
  full_name: Santini, P.
  last_name: Santini
- first_name: F.
  full_name: Arevalo-Gonzalez, F.
  last_name: Arevalo-Gonzalez
- first_name: R.
  full_name: Begley, R.
  last_name: Begley
- first_name: M.
  full_name: Castellano, M.
  last_name: Castellano
- first_name: B.
  full_name: Ciardi, B.
  last_name: Ciardi
- first_name: C. T.
  full_name: Donnan, C. T.
  last_name: Donnan
- first_name: D.
  full_name: Dottorini, D.
  last_name: Dottorini
- first_name: J. S.
  full_name: Dunlop, J. S.
  last_name: Dunlop
- first_name: S. L.
  full_name: Finkelstein, S. L.
  last_name: Finkelstein
- first_name: A.
  full_name: Fontana, A.
  last_name: Fontana
- first_name: M.
  full_name: Giavalisco, M.
  last_name: Giavalisco
- first_name: M.
  full_name: Hirschmann, M.
  last_name: Hirschmann
- first_name: I.
  full_name: Jung, I.
  last_name: Jung
- first_name: A. M.
  full_name: Koekemoer, A. M.
  last_name: Koekemoer
- first_name: V.
  full_name: Kokorev, V.
  last_name: Kokorev
- first_name: M.
  full_name: Llerena, M.
  last_name: Llerena
- first_name: R. A.
  full_name: Lucas, R. A.
  last_name: Lucas
- first_name: Sara
  full_name: Mascia, Sara
  id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
  last_name: Mascia
- first_name: E.
  full_name: Merlin, E.
  last_name: Merlin
- first_name: P. G.
  full_name: Pérez-González, P. G.
  last_name: Pérez-González
- first_name: T. M.
  full_name: Stanton, T. M.
  last_name: Stanton
- first_name: R.
  full_name: Tripodi, R.
  last_name: Tripodi
- first_name: X.
  full_name: Wang, X.
  last_name: Wang
- first_name: B. J.
  full_name: Weiner, B. J.
  last_name: Weiner
citation:
  ama: 'Napolitano L, Pentericci L, Dickinson M, et al. Lyα visibility from z = 4.5
    to 11 in the UDS field: Evidence for a high neutral hydrogen fraction and small
    ionized bubbles at z ∼ 7. <i>Astronomy and Astrophysics</i>. 2026;708. doi:<a
    href="https://doi.org/10.1051/0004-6361/202556912">10.1051/0004-6361/202556912</a>'
  apa: 'Napolitano, L., Pentericci, L., Dickinson, M., Arrabal Haro, P., Taylor, A.
    J., Calabrò, A., … Weiner, B. J. (2026). Lyα visibility from z = 4.5 to 11 in
    the UDS field: Evidence for a high neutral hydrogen fraction and small ionized
    bubbles at z ∼ 7. <i>Astronomy and Astrophysics</i>. EDP Sciences. <a href="https://doi.org/10.1051/0004-6361/202556912">https://doi.org/10.1051/0004-6361/202556912</a>'
  chicago: 'Napolitano, L., L. Pentericci, M. Dickinson, P. Arrabal Haro, A. J. Taylor,
    A. Calabrò, A. Bhagwat, et al. “Lyα Visibility from z = 4.5 to 11 in the UDS Field:
    Evidence for a High Neutral Hydrogen Fraction and Small Ionized Bubbles at z ∼
    7.” <i>Astronomy and Astrophysics</i>. EDP Sciences, 2026. <a href="https://doi.org/10.1051/0004-6361/202556912">https://doi.org/10.1051/0004-6361/202556912</a>.'
  ieee: 'L. Napolitano <i>et al.</i>, “Lyα visibility from z = 4.5 to 11 in the UDS
    field: Evidence for a high neutral hydrogen fraction and small ionized bubbles
    at z ∼ 7,” <i>Astronomy and Astrophysics</i>, vol. 708. EDP Sciences, 2026.'
  ista: 'Napolitano L, Pentericci L, Dickinson M, Arrabal Haro P, Taylor AJ, Calabrò
    A, Bhagwat A, Santini P, Arevalo-Gonzalez F, Begley R, Castellano M, Ciardi B,
    Donnan CT, Dottorini D, Dunlop JS, Finkelstein SL, Fontana A, Giavalisco M, Hirschmann
    M, Jung I, Koekemoer AM, Kokorev V, Llerena M, Lucas RA, Mascia S, Merlin E, Pérez-González
    PG, Stanton TM, Tripodi R, Wang X, Weiner BJ. 2026. Lyα visibility from z = 4.5
    to 11 in the UDS field: Evidence for a high neutral hydrogen fraction and small
    ionized bubbles at z ∼ 7. Astronomy and Astrophysics. 708, A102.'
  mla: 'Napolitano, L., et al. “Lyα Visibility from z = 4.5 to 11 in the UDS Field:
    Evidence for a High Neutral Hydrogen Fraction and Small Ionized Bubbles at z ∼
    7.” <i>Astronomy and Astrophysics</i>, vol. 708, A102, EDP Sciences, 2026, doi:<a
    href="https://doi.org/10.1051/0004-6361/202556912">10.1051/0004-6361/202556912</a>.'
  short: L. Napolitano, L. Pentericci, M. Dickinson, P. Arrabal Haro, A.J. Taylor,
    A. Calabrò, A. Bhagwat, P. Santini, F. Arevalo-Gonzalez, R. Begley, M. Castellano,
    B. Ciardi, C.T. Donnan, D. Dottorini, J.S. Dunlop, S.L. Finkelstein, A. Fontana,
    M. Giavalisco, M. Hirschmann, I. Jung, A.M. Koekemoer, V. Kokorev, M. Llerena,
    R.A. Lucas, S. Mascia, E. Merlin, P.G. Pérez-González, T.M. Stanton, R. Tripodi,
    X. Wang, B.J. Weiner, Astronomy and Astrophysics 708 (2026).
das_tickbox: '0'
date_created: 2026-10-04T22:01:55Z
date_published: 2026-04-01T00:00:00Z
date_updated: 2026-10-12T07:11:18Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1051/0004-6361/202556912
external_id:
  arxiv:
  - '2508.14171'
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fulldoi: https://doi.org/10.1051/0004-6361/202556912
has_accepted_license: '1'
intvolume: '       708'
language:
- iso: eng
month: '04'
oa: 1
oa_version: Published Version
publication: Astronomy and Astrophysics
publication_identifier:
  eissn:
  - 1432-0746
  issn:
  - 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
researchdata_availability: no
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status: public
supplementarymaterial: yes
title: 'Lyα visibility from z = 4.5 to 11 in the UDS field: Evidence for a high neutral
  hydrogen fraction and small ionized bubbles at z ∼ 7'
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type: journal_article
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