JWST IFU Maps Contrasting Electron Densities in z=9.31 Interacting Galaxy Gz9p3
Spatially resolved JWST spectroscopy of an interacting galaxy at z=9.31 shows pristine gas infall into the core after merger, producing stark density and metallicity gradients plus sub-escape outflows. Evidence rests on one NIRSpec IFU dataset; larger samples are required to generalize.
The team used NIRSpec IFU with R≈2700 to separate core and tail spectra, measuring [SII] ratios for density, strong-line diagnostics for metallicity, and [OIII] kinematics for outflows. Core gas shows rapid pristine infall diluting metallicity while driving moderate star formation; the tail retains higher metallicity and higher specific star formation. No rotation is detected, confirming a dynamically hot post-merger state. Outflow velocities remain sub-escape, implying recycled fountain gas rather than ejection. This single-system view reveals how mergers at z>9 can rapidly mix unenriched gas into galaxy centers, accelerating early enrichment cycles. The integrated spectrum averages these extremes, masking the spatial contrast that only IFU resolves. Comparable systems in CEERS and JADES show similar merger signatures but lack the density-metallicity decoupling seen here. The main limitation is the single-object sample; a statistical IFU survey of 20–30 z≈9 mergers would test whether core dilution is generic. ALMA [CII] mapping could confirm molecular inflows on <500 pc scales.
Ikeda et al.: ALMA [CII] observations of Gz9p3 will detect inflow velocities >150 km/s on 300-pc scales within 18 months.
Sources (3)
- [1]Primary Source(https://arxiv.org/abs/2608.16996)
- [2]Supporting Source(https://arxiv.org/abs/2305.03042)
- [3]Supporting Source(https://arxiv.org/abs/2401.00976)