JADES and SAPPHIRES: galaxy metamorphosis amidst a huge, luminous emission-line region

Journal article

We report the discovery of a remarkably large and luminous line-emitting nebula extending on either side of the Balmer-break galaxy JADES-GS-518794 at , detected with James Webb Space Telescope (JWST)/NIRCam imaging in [O iii]4959, 5007 and H α and spectroscopically confirmed with NIRCam/wide-field slitless spectroscopy, thanks to the pure-parallel programme Slitless Areal Pure Parallel HIgh-Redshift Emission Survey. The end-to-end velocity offset is . Nebulae with such large sizes and high luminosities (25 pkpc diameter, ) are routinely observed around bright quasars, unlike JADES-GS-518794. With a stellar mass of , this galaxy is at the knee of the mass function at . Its star formation rate declined for some time (10–100 Myr prior to observation), followed by a recent (10 Myr) upturn. This system is part of a candidate large-scale galaxy overdensity, with an excess of Balmer-break galaxies compared to the field (3σ). We discuss the possible origin of this nebula as material from a merger or gas expelled by an active galactic nucleus (AGN). The symmetry of the nebula, its bubble-like morphology, kinematics, high luminosity, and the extremely high equivalent width of [O iii] together favour the AGN interpretation. Intriguingly, there may be a physical connection between the presence of such a large, luminous nebula and the possible metamorphosis of the central galaxy towards quenching.

Authors: D’Eugenio, F; Helton, JM; Hainline, K; Sun, F; Maiolino, R

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 542
• Issue: 2
• Pages: 960-981
• Publication date: 2025-07-14
• Acceptance date: 2025-07-07
• DOI: 10.1093/mnras/staf1138
• EISSN: 1365-2966
• ISSN: 0035-8711
• Language: English
• Keywords: galaxies: high-redshift; galaxies: evolution; galaxies: formation; galaxies: active; galaxies: jets