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We present NIRSpec IFS observations of a galaxy group around the massive GS₄891 galaxy at z ∼ 3. 7 in GOODS-South that includes two other two systems, GS₄891ₙ to the north and GS₂8356 to the east. These observations, obtained as part of the GTO Galaxy Assembly – NIRSpec IFS (GA-NIFS) program, allow us to study for the first time the spatially resolved properties of the interstellar medium (ISM) and the ionised gas kinematics of a galaxy at this redshift. Leveraging the wide wavelength range spanned with the high-dispersion grating (with resolving power R = 2700) observations, covering from O II λλ 3726, 29 to S II λλ 6716, 31, we explore the spatial distribution of the star formation rate, nebular attenuation, and gas metallicity, together with the mechanisms responsible for the excitation of the ionised gas. GS₄891 presents a clear gradient of gas metallicity (as traced by 12 + log (O/H) ) by more than 0. 2 dex from the southeast (where a star-forming clump is identified) to the northwest. The gas metallicity in the less massive northern system, GS₄891ₙ, is also higher by 0. 2 dex than at the centre of GS₄891, suggesting that inflows of lower-metallicity gas might be favoured in higher-mass systems. The kinematic analysis shows that GS₄891 presents velocity gradients in the ionised gas consistent with rotation. The region between GS₄891 and GS₄891ₙ does not present high gas turbulence, which, together with the difference in gas metallicities, suggests that these two systems might be in a pre-merger stage. Finally, GS₄891 hosts an ionised outflow that extends out to r out = 1. 5 kpc from the nucleus and reaches maximum velocities, v out, of approximately 400 km s −1. Despite entraining an outflowing mass rate of Ṁ out ∼ 4 M ⊙ yr −1, the low associated mass-loading factor, η ∼ 0. 04, implies that the outflow does not have a significant impact on the star formation activity of the galaxy.
Pino et al. (Thu,) studied this question.