Discovery of a Gas-enshrouded Broad-line Active Galactic Nucleus at z ∼ 7
Year: 2026
Type: article
Abstract: The Ly α absorption profile in star-forming galaxies serves as a powerful tracer of the extended, dense neutral hydrogen in their surroundings during the Epoch of Reionization (EoR). We report a unique galaxy, A2744-z7DLA, at z ≈ 6.87, gravitationally lensed by the foreground galaxy cluster A2744, which exhibits both moderate Ly α emission and damped Ly α absorption, suggesting the presence of a dense neutral hydrogen environment. Our analysis suggests that the UV continuum turnover near Ly α is more likely shaped by a damped Ly α system rather than nebular continuum from the two-photon process. We analyze the physical properties of A2744-z7DLA with spectroscopic and photometric data from the JWST and the Hubble Space Telescope. The galaxy shows a compact morphology ( r e ∼ 0.3 kpc) and a broadened H α emission line, suggesting possible active galactic nucleus (AGN) activity. The broad component of H α has an FWHM of 2721 ± 200 km s −1 , corresponding to a black hole mass of M BH = 2.9 0 − 1.28 + 2.35 × 1 0 7 M ⊙ and a black hole to stellar mass ratio of log ( M BH / M ⊙ ) = − 1.3 1 − 0.36 + 0.37 . The Balmer decrement (H α /H β ) yields a dust attenuation of A V ≈ 1.15 ± 0.23. Furthermore, we perform spectral energy distribution fitting using both stellar and AGN models. The results show that the UV and optical wavelengths are dominated by star-forming regions, while the AGN component contributes primarily at longer wavelengths. This work provides new insights into the interplay between star formation, neutral gas, and potential AGN activity in galaxies during the EoR.
Institutions: University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing Normal University, National Astronomical Observatories, Centre National de la Recherche Scientifique, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Astrophysique, Instrumentation et Modélisation, CEA Paris-Saclay, Institut de Recherche sur les Lois Fondamentales de l'Univers, Université Paris Diderot, Peking University, Max Planck Institute for Extraterrestrial Physics, University of Copenhagen, University of Cambridge
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,400
OpenAlex ID: W7129020681
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