Shedding the envelope: JWST reveals a kiloparsec-scale [OIII]-weak Balmer shell around a z=7.64 quasar

Julien Wolf, Eduardo Bañados, Xiaohui Fan, Antoine Dumont, James E. Davies, David S. N. Rupke, Jinyi Yang, Weizhe Liu, Silvia Belladitta, Aaron Barth, Sarah Bosman, Tiago Costa, Frederick B. Davies, Roberto Decarli, Dominika Ďurovčíková, Anna-Christina Eilers, Hyunsung D. Jun, Yichen Liu, Federica Loiacono, Alessandro Lupi, Chiara Mazzucchelli, Maria Pudoka, Sofía Rojas-Ruiz, Jan-Torge Schindler, Wei Leong Tee, Benny Trakhtenbrot, Fabian Walter, Huanian Zhang

First listed 2025-12-17 | Last updated 2026-01-07

Abstract

Luminous quasars at the redshift frontier z>7 serve as stringent probes of super-massive black hole formation and they are thought to undergo much of their growth obscured by dense gas and dust in their host galaxies. Fully characterizing the symbiotic evolution of SMBHs and hosts requires rest-frame optical observations that span spatial scales from the broad-line region to the ISM and CGM. JWST now provides the necessary spatially resolved spectroscopy to do so. But the physical conditions that regulate the interplay between SMBHs and their hosts at the highest redshifts, especially the nature of early feedback phases, remain unclear. We present JWST/NIRSpec IFU observations of J0313$-$1806 at z=7.64, the most distant luminous quasar known. From the restframe optical spectrum of the unresolved quasar, we derive a black hole mass of $M_\mathrm{BH}=(1.63 \pm 0.10)\times10^9 M_\odot$ based on H$β$ and an Eddington rate of $λ=L/L_\mathrm{Edd}=0.80\pm 0.05$, consistent with previous MgII-based estimates. J0313-1806 exhibits no detectable [O III] emission on nuclear scales. Most remarkably, we detect an ionized gas shell extending out to $\sim 1.8$ kpc traced by H$β$ emission that also lacks any significant [O III], with a $3σ$ upper limit on the [O III]$ λ$5007 to H$β$ flux ratio of $\log_{10} \left( F(\mathrm{[OIII]})/F(\mathrm{H}β)\right)=-1.15$. Through photoionization modelling, we demonstrate that the extended emission is consistent with a thin, clumpy outflowing shell where [OIII] is collisionally de-excited by dense gas. We interpret this structure as a fossil remnant of a recent blowout phase, providing evidence for episodic feedback cycles in one of the earliest quasars. These findings suggest that dense ISM phases may play a crucial role in shaping the spectral properties of quasars accross cosmic time.

Short digest

JWST/NIRSpec IFU mapping of the z=7.64 quasar J0313−1806 reveals a kiloparsec-scale Hβ-bright shell (r ≈ 1.8 kpc) that is strikingly [O III]-weak, with a 3σ limit of log10([O III]/Hβ) = −1.15. The unresolved nucleus shows no detectable [O III] and yields M_BH = 1.63×10^9 Msun and λ_Edd ≈ 0.80 from Hβ. Photoionization modeling favors a thin, clumpy, dense outflowing shell where [O III] is collisionally de-excited, interpreted as a fossil of a recent blowout. This points to episodic feedback operating in one of the earliest luminous quasars and highlights dense ISM phases as key to early spectral phenomenology.

Key figures to inspect

• Figure 1: Inspect the quasar Hβ fit and strong Fe II to see how the Hβ-based M_BH and λ_Edd are anchored, and note the absence of narrow [O III] despite broad Balmer emission.
• Figure 2: Check the wavelength-dependent PSF scaling against the PSF star; this validates that extended residuals are not PSF mismatch artifacts near Hβ.
• Figure 3: Study the PSF-subtracted residual map and region A to confirm that the extended emission is real and roughly ring-like around the quasar position.
• Figure 4: Use the Hβ moment maps to trace the shell geometry: flux peaking near the quasar, a coherent velocity gradient consistent with expansion/rotation, and σ patches >600 km/s at the edges indicating turbulence in the shell.