Discovery of a Gas-enshrouded Broad-line Active Galactic Nucleus at z ∼ 7

The Lyα 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 Lyα emission and damped Lyα absorption, suggesting the presence of a dense neutral hydrogen environment. Our analysis suggests that the UV continuum turnover near Lyα is more likely shaped by a damped Lyα 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 (re ∼ 0.3 kpc) and a broadened Hα emission line, suggesting possible active galactic nucleus (AGN) activity. The broad component of Hα has an FWHM of 2721 ± 200 km s−1, corresponding to a black hole mass of MBH=2.90−1.28+2.35×107M⊙ and a black hole to stellar mass ratio of log(MBH/M⊙)=−1.31−0.36+0.37 . The Balmer decrement (Hα/Hβ) yields a dust attenuation of AV ≈ 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.