GA-NIFS: dissecting the alchemised: JWST reveals turbulent metal-poor gas fuelling a cospatial starburst in a complex system at z = 10.17

ABSTRACT Recent observations revealed that distant galaxies have bursty star formation histories, regulated by stellar or active galactic nuclei (AGNs) feedback and gas inflows. According to theoretical models, feedback preferentially removes metal-rich gas, while subsequent starbursts are triggered by mergers and newly accreted gas that is generally less enriched than the galaxy’s interstellar medium (ISM). Therefore, gas-phase metallicity provides key insights into the baryonic processes shaping early galaxies. We present the first NIRSpec/integral-field unit (IFU) study of spatially resolved ISM properties in the MACS0647-JD system ($z=10.17$). The system consists of two stellar components detected in NIRSpec/IFU (Near-InfraRed Spectrograph Integral Field Unit) and NIRCam (Near-InfraRed Camera) photometry. The main component ($\log \left(M_{\ast }/\mathrm{ M}_{\odot }\right)=7.77 \pm 0.09$; $12+\log \left(\rm O/H\right)=7.89 \pm 0.16$) is more massive and significantly more metal-rich compared to its companion ($\log \left(M_{\ast }/\mathrm{ M}_{\odot }\right)=7.42\pm 0.07$; $12+\log \left(\rm O/H\right)=7.47 \pm 0.20$), suggesting an older stellar population and a prolonged chemical enrichment history. We find that the H$\gamma$ line emission centroid is spatially offset by $\sim 0.1\,\mathrm{ arcsec}$ (150 pc in the source plane) from the stellar continuum centroid; the latter coincides with the location of the main stellar component. This offset provides possible evidence of a merger-driven starburst in this system. By comparing the spatial distributions of the metallicity, velocity dispersion, and the burstiness of star formation history, we infer the presence of turbulent, metal-poor gas outside the stellar components. This metal-poor, dynamically unstable gas is likely responsible for the enhanced recent star formation in the north-east region of the system.