Lyα emission is one of a few observable features of galaxies that can trace the neutral hydrogen content in the Universe during the Epoch of Reionization (EoR). To accomplish this, we need an efficient way to survey for Lyα emitters (LAEs) at redshifts beyond 7, requiring unbiased emission-line observations that are both sufficiently deep and wide to cover enough volume to detect them. Here we present results from PASSAGE—a pure-parallel JWST/NIRISS slitless spectroscopic survey to detect LAEs deep into the EoR, without the bias of photometric preselection. We identify four LAEs at 7.5 ≤ z ≤ 9.5 in four surveyed pointings and estimate the luminosity function (LF). We find that the LF does show a marked decrease compared to post-reionization measurements, but the change is a factor of ≲10, which is less than expected from theoretical calculations and simulations, as well as observational expectations from the pre-JWST literature. Modeling of the intergalactic medium and expected Lyα profiles implies that these galaxies reside in ionized bubbles of ⪆2 physical Mpc. We also report that in the four fields we detect {3, 1, 0, 0} LAEs, which could indicate strong field-to-field variation in the LAE distribution, consistent with a patchy H i distribution at z ∼ 8. We compare the recovered LAE number counts with expectations from simulations and discuss the potential implications for reionization and its morphology.
The JWST/PASSAGE Survey: Testing Reionization Histories with JWST's First Unbiased Survey for Lyα Emitters at Redshifts 7.5–9.5
- Creators
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Runnholm, Axel1
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Hayes, Matthew J.1
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Mehta, Vihang2, 3
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Malkan, Matthew A.4
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Scarlata, Claudia5
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Nedkova, Kalina V.6, 7
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Rafelski, Marc6, 7
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Vulcani, Benedetta8
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Huberty, Mason5
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Herenz, E. Christian9
- Hutter, Anne10
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Bruton, Sean3
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Acharyya, Ayan8
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Atek, Hakim11, 12
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Baronchelli, Ivano13
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Battisti, Andrew J.14, 15, 16
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Bradač, Maruša17, 18
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Bunker, Andrew J.19
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Dai, Y. Sophia20
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Hannahs, Clea4
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Hasan, Farhanul7
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Kim, Keunho J.2, 3
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Leethochawalit, Nicha21
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Lin, Yu-Heng2, 3
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Rutkowski, Michael J.22
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Saldana-Lopez, Alberto1
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Sattari, Zahra2, 3
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Wang, Xin23, 20, 24
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1.
Stockholm University
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2.
Infrared Processing and Analysis Center
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3.
California Institute of Technology
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4.
University of California, Los Angeles
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5.
University of Minnesota
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6.
Johns Hopkins University
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7.
Space Telescope Science Institute
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8.
Osservatorio Astronomico di Padova
- 9. Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune University Campus, Pune 411 007, India
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10.
University of Copenhagen
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11.
Institut d'Astrophysique de Paris
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12.
Sorbonne University
- 13. INAF—Istituto di Radioastronomia, Via Gobetti 101 40129 Bologna, Italy
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14.
International Centre for Radio Astronomy Research
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15.
Australian National University
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16.
Centre of Excellence for All-Sky Astrophysics
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17.
University of Ljubljana
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18.
University of California, Davis
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19.
University of Oxford
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20.
National Astronomical Observatories
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21.
National Astronomical Research Institute of Thailand
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22.
Minnesota State University, Mankato
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23.
University of Chinese Academy of Sciences
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24.
Beijing Normal University
Abstract
Copyright and License
© 2025. The Author(s). Published by the American Astronomical Society.
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Acknowledgement
This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with programs #1571 and #2079. The specific observations analyzed can be accessed via doi: 10.17909/k1a0-qg30.
M.J.H. is supported by the Swedish Research Council (Vetenskapsrådet) and is Fellow of the Knut & Alice Wallenberg Foundation. M.B. acknowledges support from the ERC grant FIRSTLIGHT and Slovenian national research agency ARIS through grants N1-0238 and P1-0188. A.A. is supported by European Union–NextGenerationEU RFF M4C2 1.1 PRIN 2022 project 2022ZSL4BL INSIGHT. A.S.-L. acknowledges support from Knut and Alice Wallenberg Foundation. H.A. acknowledges support from CNES, focused on the JWST mission, and the Programme National Cosmology and Galaxies (PNCG) of CNRS/INSU with INP and IN2P3, cofunded by CEA and CNES. A.H. acknowledges support by the VILLUM FONDEN under grant 37459. The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foundation under grant DNRF140. We thank the anonymous referee, whose thoughtful comments have enhanced the quality of the manuscript.
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Additional details
- National Aeronautics and Space Administration
- NAS 5-03127
- Swedish Research Council
- Knut and Alice Wallenberg Foundation
- European Research Council
- FIRSTLIGHT
- The Slovenian Research and Innovation Agency
- N1-0238
- The Slovenian Research and Innovation Agency
- P1-0188
- European Union
- 2022ZSL4BL INSIGHT
- Centre National d'Études Spatiales
- Villum Fonden
- 37459
- Danish National Research Foundation
- DNRF140
- Accepted
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2025-03-11
- Available
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2025-04-30Published
- Caltech groups
- Infrared Processing and Analysis Center (IPAC), Division of Physics, Mathematics and Astronomy (PMA)
- Publication Status
- Published