GA-NIFS: Dissecting the multiple sub-structures and probing their complex interactions in the Lyα emitter galaxy CR7 at z=6.6 with JWST/NIRSpec

We present JWST/NIRSpec integral field spectroscopic (IFS) observations of the Ly alpha emitter CR7 at z similar to 6.6, observed as part of the GA-NIFS program. Using low-resolution PRISM (R similar to 100) data, we confirm the observation of a bright Ly alpha emitter with a diffuse Ly alpha halo extending up to 3 kpc from the peak of ionised emission. Both features are associated with the most massive UV bright galaxy in the system, CR7-A. We confirm the presence of two additional UV-bright satellites (CR7-B and CR7-C) detected at projected distances of 6.4 and 5.2 kpc from the primary source. We performed a spectral energy distribution fitting of the low-resolution data, and it revealed an inverted star formation history between two satellites at early epochs and a spatially resolved anti-correlation of the gas-phase metallicity and the star formation rate density, likely driven by the gas exchange among the satellites and favouring the merger scenario for CR7. From the high-resolution G395H (R similar to 2700) data, we discovered at least one additional companion mainly traced by the [O III]lambda 5007 emission line, although it is not detected in continuum emission. We disentangled the kinematics of the system and reveal extended ionised emission linking the main galaxy and the satellite. We spatially resolved the [O III]lambda 5007, [O III]4363, and H gamma emission lines and used a diagnostic diagram tailored to high-z systems to reveal tentative evidence of active galactic nucleus ionisation across the main galaxy (CR7-A) and the N-E companion (CR7-B). Moreover, we detected an unresolved blueshifted outflow from one of the satellites and present first evidence for a redshifted outflow from the main galaxy. Finally, we computed the resolved electron temperature (T-e similar to 1.6x10(4) K) and metallicity maps (log(Z/Z(circle dot)) from -0.8 to -0.5), and we provide insights on how the physical properties of the system evolved at earlier epochs.