Abstract We present JWST/NIRSpec IFU observations of the z = 7.152 galaxy system B14-65666, as part of the GA-NIFS survey. Line and continuum emission in this massive system (log10(M*/M⊙) = 9.8 ± 0.2) is resolved into two strong cores surrounded by diffuse emission, as seen in recent JWST/NIRCam imaging. Our dataset contains detections of OIIλλ3726, 3729, NeIIIλλ3869, 3968, Balmer lines, OIIIλλ4959, 5007, HeIλ5875, and weak OIIIλ4363. Each spectrum is fit with a model that consistently incorporates interstellar medium conditions (i.e., electron temperature, Te, electron density, ne, and colour excess, E(B − V)). The resulting line fluxes are used to constrain the gas-phase metallicity (Zg ~ 0.2 − 0.3 solar) and Hβ-based SFR for each region. Common line ratio diagrams (O32-R23, R3-R2, Ne3O2-R23) reveal that each line-emitting region lies at the intersection of low- and high-redshift galaxies, suggesting low ionisation and higher metallicity compared to the predominantly lower-mass galaxies studied with the JWST/NIRSpec IFU so far at z 5.5. Spaxel-by-spaxel fits reveal evidence for both narrow (FWHM 400 km s−1) and broad (FWHM 500 km s−1) line emission, the latter of which likely represents tidal interaction or outflows. Comparison to ALMA C II158μm and O III88μm data shows a similar velocity structure, and we explore optical-far infrared diagnostics. The two core galaxies both lie on the mass-metallicity relation at z 4, but show contrasting properties (e.g., M*, Zg), suggesting distinct evolutionary pathways. Combining the NIRSpec IFU and ALMA datasets, our analysis opens new windows into the merging system B14-65666.
Jones et al. (Tue,) studied this question.