---
OA_place: publisher
OA_type: gold
_id: '21710'
abstract:
- lang: eng
text: "Early results from JWST suggest that Epoch of Reionization (EoR) galaxies
produce copious ionizing photons, which, if they escape efficiently, could cause
reionization to occur too early. We study this problem using JWST imaging and
prism spectroscopy for 412 galaxies at 4.5 < z < 9.0. We fit these data simultaneously
with stellar population and nebular emission models that include a parameter for
the fraction of ionizing photons that escape the galaxy, fesc. We find that the
ionization production efficiency, ξion = Q(H0)/LUV, increases with redshift and
decreasing UV luminosity, but shows significant scatter, (log ion z, MUV) 0.3
dex. The inferred escape fractions averaged over the population are low, ranging
from〈fesc〉 ≃ 2.6% ± 1.4% at 6 < z < 9 to 6.5% ± 2.2% at 4.5 < z < 6, with weak
or no indication of evolution with redshift. This implies that in our models most
of the ionizing photons need to be absorbed to account for the nebular emission.
We compute the impact of our results on reionization, including the distributions
for ξion and fesc, and the evolution and uncertainty of the UV luminosity function.
Considering galaxies brighter than MUV < −16 mag would produce an intergalactic
medium hydrogen-ionized fraction of xe = 0.5 at 5.3 < z < 5.8, possibly too late
compared to constraints from from quasistellar\r\nobject (QSO) sight lines. Including
fainter galaxies, MUV < −14 mag, we obtain xe = 0.5 at 6.0 < z < 8.1, fully consistent
with QSO and cosmic microwave background data. This implies that EoR galaxies
produce plenty of ionizing photons, but that these do not efficiently escape.
This may be a result of high gas column densities combined with burstier star
formation histories, which limit the time massive stars are able to clear channels
through the gas for ionizing photons to escape."
acknowledgement: "We wish to thank our colleagues in the CEERS collaboration for their
hard work and valuable contributions on this project. We extend our sincerest thanks
to the anonymous referee whose critical and constructive report improved the quality
of this manuscript. We also thank the JADES team for providing an excellent dataset
for science. We with to thank colleagues for valuable discussions, feedback, and
suggestions, including John Chisholm, Kevin Huffenberger, Jessica\r\nMeh, Julian
Muñoz, Irene Shivaei, Justin Spilker, Aaron Smith, and Romain Teyssier.\r\nPortions
of this research were conducted with the advanced computing resources provided by
Texas A&M High Performance Research Computing (HPRC, http://hprc.tamu.edu). This
work benefited from support from the George P. and Cynthia Woods Mitchell Institute
for Fundamental Physics and Astronomy at Texas A&M University. CP thanks Marsha
and Ralph Schilling for generous support of this research. This work was partially
support by the Future Investigators in NASA Earth and Space Science and Technology
(FINESST) program grant No. 80NSSC23K1487. R.A. acknowledges support of grant PID2023-147386NB-I00
funded by MICIU/AEI/10.13039/501100011033 and by ERDF/EU, and the Severo Ochoa grant
CEX2021-001131-S funded by MCIN/AEI/10.13039/50110001103. A.C.C. acknowledges support
from a UKRI Frontier Research Guarantee Grant (PI Carnall; grant reference EP/Y037065/1)
This work acknowledges support from the NASA/ESA/CSA James Webb Space Telescope
through the\r\nSpace Telescope Science Institute, which is operated by the Association
of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-03127.
Support for program JWST-ERS-01345.009-A, JWST-GO-02079.013-A, JWST-GO-06368.011-A,
and JWST-GO-01837.030-A, was provided by NASA through a grant from the Space Telescope
Science Institute, which is operated by the Association of Universities for Research
in Astronomy, Inc., under NASA contract NAS 5-03127. This work made use of v2.2
of the Binary Population\r\nand Spectral Synthesis (BPASS) models as described in
E. R. Stanway & J. J. Eldridge (2018)."
article_number: '111'
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Casey
full_name: Papovich, Casey
last_name: Papovich
- first_name: Justin W.
full_name: Cole, Justin W.
last_name: Cole
- first_name: Weida
full_name: Hu, Weida
last_name: Hu
- first_name: Steven L.
full_name: Finkelstein, Steven L.
last_name: Finkelstein
- first_name: Lu
full_name: Shen, Lu
last_name: Shen
- first_name: Pablo
full_name: Arrabal Haro, Pablo
last_name: Arrabal Haro
- first_name: Ricardo O.
full_name: Amorín, Ricardo O.
last_name: Amorín
- first_name: Bren E.
full_name: Backhaus, Bren E.
last_name: Backhaus
- first_name: Micaela B.
full_name: Bagley, Micaela B.
last_name: Bagley
- first_name: Rachana
full_name: Bhatawdekar, Rachana
last_name: Bhatawdekar
- first_name: Antonello
full_name: Calabrò, Antonello
last_name: Calabrò
- first_name: Adam C.
full_name: Carnall, Adam C.
last_name: Carnall
- first_name: Nikko J.
full_name: Cleri, Nikko J.
last_name: Cleri
- first_name: Emanuele
full_name: Daddi, Emanuele
last_name: Daddi
- first_name: Mark
full_name: Dickinson, Mark
last_name: Dickinson
- first_name: Norman A.
full_name: Grogin, Norman A.
last_name: Grogin
- first_name: Benne W.
full_name: Holwerda, Benne W.
last_name: Holwerda
- first_name: Anne E.
full_name: Jaskot, Anne E.
last_name: Jaskot
- first_name: Anton M.
full_name: Koekemoer, Anton M.
last_name: Koekemoer
- first_name: Mario
full_name: Llerena, Mario
last_name: Llerena
- first_name: Ray A.
full_name: Lucas, Ray A.
last_name: Lucas
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: Fabio
full_name: Pacucci, Fabio
last_name: Pacucci
- first_name: Laura
full_name: Pentericci, Laura
last_name: Pentericci
- first_name: Pablo G.
full_name: Pérez-González, Pablo G.
last_name: Pérez-González
- first_name: Nor
full_name: Pirzkal, Nor
last_name: Pirzkal
- first_name: Srinivasan
full_name: Raghunathan, Srinivasan
last_name: Raghunathan
- first_name: Lise Marie
full_name: Seillé, Lise Marie
last_name: Seillé
- first_name: Rachel S.
full_name: Somerville, Rachel S.
last_name: Somerville
- first_name: L. Y.Aaron
full_name: Yung, L. Y.Aaron
last_name: Yung
citation:
ama: Papovich C, Cole JW, Hu W, et al. Galaxies in the epoch of reionization are
all bark and no bite-plenty of ionizing photons, low escape fractions. The
Astrophysical Journal. 2026;1000(1). doi:10.3847/1538-4357/ae3b25
apa: Papovich, C., Cole, J. W., Hu, W., Finkelstein, S. L., Shen, L., Arrabal Haro,
P., … Yung, L. Y. A. (2026). Galaxies in the epoch of reionization are all bark
and no bite-plenty of ionizing photons, low escape fractions. The Astrophysical
Journal. IOP Publishing. https://doi.org/10.3847/1538-4357/ae3b25
chicago: Papovich, Casey, Justin W. Cole, Weida Hu, Steven L. Finkelstein, Lu Shen,
Pablo Arrabal Haro, Ricardo O. Amorín, et al. “Galaxies in the Epoch of Reionization
Are All Bark and No Bite-Plenty of Ionizing Photons, Low Escape Fractions.” The
Astrophysical Journal. IOP Publishing, 2026. https://doi.org/10.3847/1538-4357/ae3b25.
ieee: C. Papovich et al., “Galaxies in the epoch of reionization are all
bark and no bite-plenty of ionizing photons, low escape fractions,” The Astrophysical
Journal, vol. 1000, no. 1. IOP Publishing, 2026.
ista: Papovich C, Cole JW, Hu W, Finkelstein SL, Shen L, Arrabal Haro P, Amorín
RO, Backhaus BE, Bagley MB, Bhatawdekar R, Calabrò A, Carnall AC, Cleri NJ, Daddi
E, Dickinson M, Grogin NA, Holwerda BW, Jaskot AE, Koekemoer AM, Llerena M, Lucas
RA, Mascia S, Pacucci F, Pentericci L, Pérez-González PG, Pirzkal N, Raghunathan
S, Seillé LM, Somerville RS, Yung LYA. 2026. Galaxies in the epoch of reionization
are all bark and no bite-plenty of ionizing photons, low escape fractions. The
Astrophysical Journal. 1000(1), 111.
mla: Papovich, Casey, et al. “Galaxies in the Epoch of Reionization Are All Bark
and No Bite-Plenty of Ionizing Photons, Low Escape Fractions.” The Astrophysical
Journal, vol. 1000, no. 1, 111, IOP Publishing, 2026, doi:10.3847/1538-4357/ae3b25.
short: C. Papovich, J.W. Cole, W. Hu, S.L. Finkelstein, L. Shen, P. Arrabal Haro,
R.O. Amorín, B.E. Backhaus, M.B. Bagley, R. Bhatawdekar, A. Calabrò, A.C. Carnall,
N.J. Cleri, E. Daddi, M. Dickinson, N.A. Grogin, B.W. Holwerda, A.E. Jaskot, A.M.
Koekemoer, M. Llerena, R.A. Lucas, S. Mascia, F. Pacucci, L. Pentericci, P.G.
Pérez-González, N. Pirzkal, S. Raghunathan, L.M. Seillé, R.S. Somerville, L.Y.A.
Yung, The Astrophysical Journal 1000 (2026).
date_created: 2026-04-12T22:01:49Z
date_published: 2026-03-20T00:00:00Z
date_updated: 2026-05-04T10:44:57Z
day: '20'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.3847/1538-4357/ae3b25
external_id:
arxiv:
- '2505.08870'
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oa_version: Published Version
publication: The Astrophysical Journal
publication_identifier:
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- 1538-4357
issn:
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publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
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status: public
title: Galaxies in the epoch of reionization are all bark and no bite-plenty of ionizing
photons, low escape fractions
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legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
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