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

¹ Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
² Steward Observatory, University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85719, USA
³ Department of Physics, Rhodes College, 2000 North Parkway, Memphis, TN 38112, USA
⁴ Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr 12-14, D-69120 Heidelberg, Germany
⁵ Department of Astronomy, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109, USA
⁶ Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697-4575, USA
⁷ Institute for Theoretical Physics, Heidelberg University, Philosophenweg 12, D-69120 Heidelberg, Germany
⁸ School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
⁹ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, I-40129 Bologna, Italy
¹⁰ MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
¹¹ Department of Physics, Northwestern College, 101 7th St SW, Orange City, IA 51041, USA
¹² School of Physics, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 02455, Republic of Korea
¹³ Como Lake Center for Astrophysics, DiSAT, Università degli Studi dell’Insubria, Via Valleggio 11, I-22100 Como, Italy
¹⁴ INFN, Sezione Milano-Bicocca, P.za della Scienza 3, I-20126 Milano, Italy
¹⁵ Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Avenida Ejercito Libertador 441, Santiago, Chile
¹⁶ Department of Physics and Astronomy, University of California, Los Angeles, 430 Portola Plaza, Los Angeles, CA 90095, USA
¹⁷ Hamburg Observatory, Gojenbergsweg 112, D-21029 Hamburg, Germany
¹⁸ School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
¹⁹ Department of Astronomy, School of Physics, Huazhong University of Science and Technology, Luoyu Road, Wuhan, 430074 Hubei, China

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Received: 1 November 2025
Accepted: 9 January 2026

Abstract

Luminous quasars at the redshift frontier z > 7 serve as stringent probes of super-massive black hole (SMBH) 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 (BLR) to the interstellar and circumgalactic medium (ISM and CGM). The James Webb Space Telescope (JWST) now provides the necessary spatially resolved spectroscopy to do so. However, 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 integral field unit (IFU) observations of J0313−1806 at z = 7.64, the most distant luminous quasar known. From the rest-frame optical spectrum of the unresolved quasar, we derived a black hole mass of M_BH = (1.63 ± 0.10)×10⁹ M_⊙ based on Hβλ4861 (Hβ) and an Eddington rate of λ = L/L_Edd = 0.80 ± 0.05, consistent with previous Mg IIλ2800-based estimates. J0313–1806 exhibits no detectable [O III] λλ4959, 5007 emission on nuclear scales (3σ upper limit equivalent width of [O III] λ5007 < 1.42 Å). Most remarkably, we did detect an ionized gas shell extending out to ∼1.8 kpc traced by Hβ emission that also lacks any significant [O III] λλ4959, 5007, with a 3σ upper limit on the [O III] λ5007 to Hβ flux ratio of log₁₀(F([O III])/F(Hβ)) = −1.15. Through photoionization modeling, we demonstrate that the extended emission is consistent with a thin, clumpy outflowing shell where [O III] 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 across cosmic time.