Probing Direct Contributions of Galaxies and Active Galactic Nuclei to Cosmic Reionization in a Quasar Field J0226+0302 with JWST/NIRCam and NIRSpec
Year: 2026
Type: article
Abstract: We present JWST Cycle 2 NIRCam and NIRSpec observations of a quasar field J0226+0302 at z = 6.5412 to probe the direct connections between the intergalactic medium (IGM), galaxies, and active galactic nuclei (AGN) during reionization. This field was previously observed by the JWST ASPIRE program, detecting eight [O III ]-emitting galaxies at 5.3 < z < 6.4 with a single NIRCam pointing. Using new NIRCam and NIRSpec observations, we identify 65 additional line-emitting galaxies at 5.3 < z < 6.4. The IGM–galaxy cross-correlation function shows an ∼2 σ excess IGM transmission at ∼10–40 cMpc from galaxies, suggesting a significant contribution from regions traced by star-forming galaxies to the local ionizing background. The IGM–galaxy cross-correlation function in this field is consistent with THESAN simulations for an IGM neutral fraction of 5%–7% and an average galaxy ionizing escape fraction f esc of 6%, although a single field is subject to substantial cosmic variance and cannot constrain these quantities independently. Among 49 line-emitting galaxies observed by NIRSpec, we identify four AGN with broad H α emission lines, resulting in an AGN fraction of 8% ± 4%. From the IGM effective optical depth and the IGM–AGN cross-correlation function, we find that the IGM transmission is higher within 5 h −1 cMpc of four AGN than around the majority of [O iii ] emitters. We interpret the excess transmission as resulting from the local radiation enhancement by the AGN, and estimate AGN f esc ∼ 50%–100%, based on our illustrative model for the IGM–AGN cross-correlation function. Future JWST/NIRSpec observations of quasar fields will yield a more constraining IGM–AGN cross-correlation function, providing further insights into the roles of galaxies and AGN in reionization.
Source: The Astrophysical Journal
Authors: Xiangyu Jin, Jinyi Yang, Feige Wang, Koki Kakiichi, Xiaohui Fan, Enrico Garaldi, Jaclyn B. Champagne, George D. Becker, Yongda Zhu, Yunjing Wu, Marianne Vestergaard, Huanqing Chen, Valentina D’Odorico, Anna-Christina Eilers, Jiamu Huang, Hyunsung D. Jun, Mingyu Li, Maria Pudoka, Wei Leong Tee, Minghao Yue, Huanian Zhang, Siwei Zou
Institutions: University of Arizona, University of Michigan, University of Copenhagen, The University of Tokyo, University of California System, University of Alberta, Institute for Fundamental Physics of the Universe, National Institute for Astrophysics, Massachusetts Institute of Technology, Korea Institute for Advanced Study, Tsinghua University, Pennsylvania State University, Huazhong University of Science and Technology, Chinese Academy of Sciences, Chinese Academy of Science South America Center for Astronomy, University of Chile
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: National Science Foundation, National Aeronautics and Space Administration, Villum Fonden, Space Telescope Science Institute, University of Alberta, National Research Foundation, Danmarks Grundforskningsfond, Chinese Academy of Sciences, Natural Sciences and Engineering Research Council of Canada, Japan Society for the Promotion of Science
Awards: G103270039, G1338664626, G17517032, ASPIRE - A Legacy Survey of Quasars in the Epoch of Reionization, G256731684, G3155054284, Formation Processes of Heavy Elements in the Early Universe Elucidated by Superconducting Nanoelectronics, Large-Scale Numerical Simulations, and Data Science, G5568641063, G6074392246, G6278171916, G7211033830
OpenAlex ID: W7223093564