Year: 2024
Type: article
Abstract: The resonant scattering interaction between Lyα photons and neutral hydrogen implies that a partially neutral intergalactic medium has the ability to significantly impact the detectability of Lyα emission in galaxies. Thus, the redshift evolution of the Lyα equivalent width distribution of galaxies offers a key observational probe of the degree of ionization during the Epoch of Reionization (EoR). Previous in-depth investigations at z ≥ 7 were limited by ground-based instrument capabilities. We present an extensive study of the evolution of Lyα emission from galaxies at 4.5 < z < 8.5, observed as part of the CEERS and JADES surveys in the JWST NIRSpec/PRISM configuration. The sample consists of 235 galaxies in the redshift range of 4.1 < z < 9.9. We identified 65 of them as Lyα emitters. We first measured the Lyα escape fractions from Lyα to Balmer line flux ratios and explored the correlations with the inferred galaxies’ physical properties, which are similar to those found at lower redshift. We also investigated the possible connection between the escape of Lyα photons and the inferred escape fractions of LyC photons obtained from indirect indicators, finding no secure correlation. We then analyzed the redshift evolution of the Lyα emitter fraction, finding lower average values at z = 5 and 6 compared to previous ground-based observations. At z = 7, the GOODS-S results are aligned with previous findings, whereas the visibility in the EGS field appears to be enhanced. This discrepancy in Lyα visibility between the two fields could potentially be attributed to the presence of early reionized regions in the EGS. Such a broad variance is also expected in the Cosmic Dawn II radiation-hydrodynamical simulation. The average Lyα emitter fraction obtained from the CEERS+JADES data continues to increase from z = 5 to 7, ultimately declining at z = 8. This suggests a scenario in which the ending phase of the EoR is characterized by ∼1 pMpc ionized bubbles around a high fraction of moderately bright galaxies. Finally, we characterize such two ionized regions found in the EGS at z = 7.18 and z = 7.49 by estimating the radius of the ionized bubble that each of the spectroscopically-confirmed members could have created.
Authors: L. Napolitano, L. Pentericci, P. Santini, A. Calabrò, S. Mascia, M. Llerena, M. Castellano, M. Dickinson, S. L. Finkelstein, R. Amorín, P. Arrabal Haro, M. Bagley, R. Bhatawdekar, N. J. Cleri, K. Davis, J. P. Gardner, E. Gawiser, M. Giavalisco, N. Hathi, B. W. Holwerda, W. Hu, I. Jung, J. S. Kartaltepe, A. M. Koekemoer, R. L. Larson, E. Merlin, B. Mobasher, C. Papovich, H. Park, N. Pirzkal, J. R. Trump, S. M. Wilkins, L. Y. A. Yung
Institutions: Astronomical Observatory of Rome, Sapienza University of Rome, University of Rome Tor Vergata, NSF NOIRLab, The University of Texas at Austin, Fundacion Agencia Aragonesa para la Investigacion y el Desarrollo, Centro de Estudios de Física del Cosmos de Aragón, University of La Serena, European Space Agency, European Space Astronomy Centre, Texas A&M University, University of Connecticut, Goddard Space Flight Center, Rutgers, The State University of New Jersey, University of Massachusetts Amherst, Space Telescope Science Institute, University of Louisville, Rochester Institute of Technology, University of California, Riverside, Lawrence Berkeley National Laboratory, University of Sussex, University of Malta
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funder: European Commission
Award: G972786147
OpenAlex ID: W6941067596
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