EIGER. VII. The evolving relationship between galaxies and the intergalactic medium in the final stages of reionization

article EIGER. VII. The evolving relationship between galaxies and the intergalactic medium in the final stages of reionization published yes Daichi Kashino author Simon J. Lilly author Jorryt J Matthee author 7439a258-f3c0-11ec-9501-9df22fe067200000-0003-2871-127X Ruari Mackenzie author Anna-Christina Eilers author Rongmon Bordoloi author Robert A. Simcoe author Rohan P. Naidu author Minghao Yue author Bin Liu author JoMa department Young galaxies as tracers and agents of cosmic reionization project We present a comprehensive analysis of the relationship between galaxies and the intergalactic medium (IGM) during the late stages of cosmic reionization, based on the complete JWST EIGER dataset. Using deep NIRCam 3.5 μm slitless spectroscopy, we construct a sample of 948 [O iii]λ5008-emitting galaxies with −21.4 ≲ MUV ≲ −17.2 spanning 5.33 < z < 6.97 along six quasar sight lines. We correlate these galaxies with Lyα and Lyβ transmission measured from high-resolution quasar spectra across multiple redshift intervals. We find clear redshift evolution in the correlation between galaxy density and transmission: it is suppressed in overdense regions at z < 5.50, while enhanced at 5.70 < z < 6.15. The intermediate range exhibits a transitional behavior. Cross-correlation measurements further reveal excess absorption within ∼8 cMpc of galaxies at low redshifts, and enhanced transmission at intermediate scales (∼5–20 cMpc) at z > 5.70. Statistical tests using mock catalogs with realistic galaxy clustering but no correlation with the transmission field confirm that the observed correlations are unlikely to arise by chance. The evolving signals can be explained by stronger absorption in overdense regions, combined with the competing influences of local radiation fields and the rising background radiation. While local radiation dominates ionization of the surrounding IGM at earlier times, the background becomes increasingly important, eventually surpassing the impact of nearby galaxies. These results support an inside-out progression of reionization, with ionized regions originating around clustered, star-forming galaxies and gradually extending into underdense regions. https://research-explorer.ista.ac.at/download/23117/23138/2026_AstrophysicalJour_Kashino.pdf application/pdfno https://creativecommons.org/licenses/by/4.0/ IOP Publishing2026 eng The Astrophysical Journal 0004-637X 1538-4357 2506.0312110.3847/1538-4357/ae2799 9972 D. Kashino et al., “EIGER. VII. The evolving relationship between galaxies and the intergalactic medium in the final stages of reionization,” The Astrophysical Journal, vol. 997, no. 2. IOP Publishing, 2026. Kashino D, Lilly SJ, Matthee JJ, Mackenzie R, Eilers A-C, Bordoloi R, Simcoe RA, Naidu RP, Yue M, Liu B. 2026. EIGER. VII. The evolving relationship between galaxies and the intergalactic medium in the final stages of reionization. The Astrophysical Journal. 997(2), 280. Kashino D, Lilly SJ, Matthee JJ, et al. EIGER. VII. The evolving relationship between galaxies and the intergalactic medium in the final stages of reionization. The Astrophysical Journal. 2026;997(2). doi:<a href="https://doi.org/10.3847/1538-4357/ae2799">10.3847/1538-4357/ae2799</a> Kashino, Daichi, Simon J. Lilly, Jorryt J Matthee, Ruari Mackenzie, Anna-Christina Eilers, Rongmon Bordoloi, Robert A. Simcoe, Rohan P. Naidu, Minghao Yue, and Bin Liu. “EIGER. VII. The Evolving Relationship between Galaxies and the Intergalactic Medium in the Final Stages of Reionization.” The Astrophysical Journal. IOP Publishing, 2026. <a href="https://doi.org/10.3847/1538-4357/ae2799">https://doi.org/10.3847/1538-4357/ae2799</a>. D. Kashino, S.J. Lilly, J.J. Matthee, R. Mackenzie, A.-C. Eilers, R. Bordoloi, R.A. Simcoe, R.P. Naidu, M. Yue, B. Liu, The Astrophysical Journal 997 (2026). Kashino, D., Lilly, S. J., Matthee, J. J., Mackenzie, R., Eilers, A.-C., Bordoloi, R., … Liu, B. (2026). EIGER. VII. The evolving relationship between galaxies and the intergalactic medium in the final stages of reionization. The Astrophysical Journal. IOP Publishing. <a href="https://doi.org/10.3847/1538-4357/ae2799">https://doi.org/10.3847/1538-4357/ae2799</a> Kashino, Daichi, et al. “EIGER. VII. The Evolving Relationship between Galaxies and the Intergalactic Medium in the Final Stages of Reionization.” The Astrophysical Journal, vol. 997, no. 2, 280, IOP Publishing, 2026, doi:<a href="https://doi.org/10.3847/1538-4357/ae2799">10.3847/1538-4357/ae2799</a>. 231172026-10-12T12:17:25Z2026-10-14T08:12:05Z