Resolving the interstellar medium in star-forming galaxies at z above 3 with the GA-NIFS survey

Bruno Rodriguez del Pino (CAB, Madrid)

Abstract: The GA-NIFS survey provides Integral Field Spectroscopic observations with NIRSpec at the JWST of a sample of around 50 galaxies from redsfhit z ~3 to ~9. These data are allowing us to characterize the internal structure of these galaxies as well as to constrain the physical processes driving galaxy evolution at an epoch when the Universe was less than ~2 Gyr old. The targets are selected among the brightest and most extended star-forming galaxies and AGN/QSO discovered so far in the distant Universe. The main goals of these observations are: to trace the distribution of star formation, to map the resolved properties of the stellar populations, to trace the gas kinematics and, therefore, determine dynamical masses and also identify non-virial motions (outflow and inflows), and to map metallicity gradients and dust extinction. In this seminar, I will describe recent results of the GA-NIFS survey and will present the detailed study of the interstellar medium and gas kinematics in a highly star-forming galaxy group at z~3.7. Analyses of the rest-frame optical emission lines have revealed a clear gradient of more than 0.2 dex in the gas metallicity from the south to the north-west of the most-massive system, suggesting ongoing accretion of low-metallicity gas from the inter-galactic medium that would be contributing to the mass-assembly of the system. The even higher gas metallicity in the lower-mass companion at the north also indicates that the accretion of low-metallicity gas is favored in the most-massive system, already suggesting a different evolution in the metallicity of satellites and centrals at high redshift. Moreover, this galaxy is host to a metal-enriched, nuclear ionized outflow that reaches up to ~1.2 kpc and could be contributing to the observed metallicity gradient. This study demonstrates the potential of IFS observations with NIRSpec to shed more light on the formation of galaxy groups and the assembly of stellar mass in the first Gyrs of the Universe.