Chasing the Beginning of Reionization in the JWST Era
Recent JWST observations at z > 6 may imply galactic ionizing photon production above prior expectations. Under observationally motivated assumptions about escape fractions, these suggest a z ~ 8–9 end to reionization, in tension with the z < 6 end required by the Ly α forest. In this work,...
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2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ada152 |
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| author | Christopher Cain Garett Lopez Anson D’Aloisio Julian B. Muñoz Rolf A. Jansen Rogier A. Windhorst Nakul Gangolli |
| author_facet | Christopher Cain Garett Lopez Anson D’Aloisio Julian B. Muñoz Rolf A. Jansen Rogier A. Windhorst Nakul Gangolli |
| author_sort | Christopher Cain |
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| description | Recent JWST observations at z > 6 may imply galactic ionizing photon production above prior expectations. Under observationally motivated assumptions about escape fractions, these suggest a z ~ 8–9 end to reionization, in tension with the z < 6 end required by the Ly α forest. In this work, we use radiative transfer simulations to understand what different observations tell us about when reionization ended and when it started. We consider a model that ends too early ( z _end ≈ 8) alongside two more realistic scenarios with z _end ≈ 5: one starting late ( z ~ 9) and another early ( z ~ 13). We find that the latter requires up to an order-of-magnitude evolution in galaxy ionizing properties at 6 < z < 12, perhaps in tension with measurements of ξ _ion by JWST, which indicate little evolution. We study how these models compare to recent measurements of the Ly α forest opacity, mean free path, intergalactic medium thermal history, visibility of z > 8 Ly α emitters, and the patchy kSZ signal from the cosmic microwave background (CMB). We find that neither of the late-ending scenarios is strongly disfavored by any single data set. However, a majority of observables, spanning several distinct types of observations, prefer a late start. Not all probes agree with this conclusion, hinting at a possible lack of concordance arising from deficiencies in observations and/or theoretical modeling. Observations by multiple experiments (including JWST, Roman, and CMB-S4) in the coming years will establish a concordance picture of reionization's beginning or uncover such deficiencies. |
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| institution | Kabale University |
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| language | English |
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| spelling | doaj-art-4f24a6ae961340ebb0d5a16b25a07d452025-02-05T14:02:16ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198018310.3847/1538-4357/ada152Chasing the Beginning of Reionization in the JWST EraChristopher Cain0https://orcid.org/0000-0001-9420-7384Garett Lopez1Anson D’Aloisio2Julian B. Muñoz3https://orcid.org/0000-0002-8984-0465Rolf A. Jansen4https://orcid.org/0000-0003-1268-5230Rogier A. Windhorst5https://orcid.org/0000-0001-8156-6281Nakul Gangolli6School of Earth and Space Exploration, Arizona State University , Tempe, AZ 85287-6004, USA ; clcain3@asu.eduDepartment of Physics and Astronomy, University of California , Riverside, CA 92521, USADepartment of Physics and Astronomy, University of California , Riverside, CA 92521, USADepartment of Astronomy, The University of Texas at Austin , 2515 Speedway, Stop C1400, Austin, TX 78712, USASchool of Earth and Space Exploration, Arizona State University , Tempe, AZ 85287-6004, USA ; clcain3@asu.eduSchool of Earth and Space Exploration, Arizona State University , Tempe, AZ 85287-6004, USA ; clcain3@asu.eduDepartment of Physics and Astronomy, University of California , Riverside, CA 92521, USARecent JWST observations at z > 6 may imply galactic ionizing photon production above prior expectations. Under observationally motivated assumptions about escape fractions, these suggest a z ~ 8–9 end to reionization, in tension with the z < 6 end required by the Ly α forest. In this work, we use radiative transfer simulations to understand what different observations tell us about when reionization ended and when it started. We consider a model that ends too early ( z _end ≈ 8) alongside two more realistic scenarios with z _end ≈ 5: one starting late ( z ~ 9) and another early ( z ~ 13). We find that the latter requires up to an order-of-magnitude evolution in galaxy ionizing properties at 6 < z < 12, perhaps in tension with measurements of ξ _ion by JWST, which indicate little evolution. We study how these models compare to recent measurements of the Ly α forest opacity, mean free path, intergalactic medium thermal history, visibility of z > 8 Ly α emitters, and the patchy kSZ signal from the cosmic microwave background (CMB). We find that neither of the late-ending scenarios is strongly disfavored by any single data set. However, a majority of observables, spanning several distinct types of observations, prefer a late start. Not all probes agree with this conclusion, hinting at a possible lack of concordance arising from deficiencies in observations and/or theoretical modeling. Observations by multiple experiments (including JWST, Roman, and CMB-S4) in the coming years will establish a concordance picture of reionization's beginning or uncover such deficiencies.https://doi.org/10.3847/1538-4357/ada152ReionizationIntergalactic mediumQuasar absorption line spectroscopyLyα forestCosmic microwave background radiationGalaxy evolution |
| spellingShingle | Christopher Cain Garett Lopez Anson D’Aloisio Julian B. Muñoz Rolf A. Jansen Rogier A. Windhorst Nakul Gangolli Chasing the Beginning of Reionization in the JWST Era The Astrophysical Journal Reionization Intergalactic medium Quasar absorption line spectroscopy Lyα forest Cosmic microwave background radiation Galaxy evolution |
| title | Chasing the Beginning of Reionization in the JWST Era |
| title_full | Chasing the Beginning of Reionization in the JWST Era |
| title_fullStr | Chasing the Beginning of Reionization in the JWST Era |
| title_full_unstemmed | Chasing the Beginning of Reionization in the JWST Era |
| title_short | Chasing the Beginning of Reionization in the JWST Era |
| title_sort | chasing the beginning of reionization in the jwst era |
| topic | Reionization Intergalactic medium Quasar absorption line spectroscopy Lyα forest Cosmic microwave background radiation Galaxy evolution |
| url | https://doi.org/10.3847/1538-4357/ada152 |
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