James Webb Space Telescope Feed Post

GA-NIFS: co-evolution within a highly star-forming galaxy group at z=3.7 witnessed by JWST/NIRSpec IFS Published: 9/25/2023 9:00:07 PM Updated: 9/25/2023 9:00:07 PM

Paper abstract: We present NIRSpec IFS observations of a galaxy group around the massiveGS_4891 galaxy at z=3.7 in GOODS-South that includes two other two systems,GS_4891_n to the north and GS_28356 to the east. These observations, obtainedas part of the GTO GA-NIFS program, allow for the first time to study thespatially resolved properties of the interstellar medium (ISM) and ionized gaskinematics of a galaxy at this redshift. Leveraging the wide wavelength rangespanned with the high-dispersion grating (with resolving power R=2700)observations, covering from [OII]\lambda\lambda3726,29 to[SII]\lambda\lambda6716,31, we explore the spatial distribution ofstar-formation rate, nebular attenuation and gas metallicity, together with themechanisms responsible for the excitation of the ionized gas. GS_4891 presentsa clear gradient of gas metallicity (as traced by 12 + log(O/H)) by more than0.2dex from the south-east (where a star-forming clump is identified) to thenorth-west. The gas metallicity in the less-massive northern system, GS_4891_n,is also higher by 0.2 dex than at the center of GS_4891, suggesting thatinflows of lower-metallicity gas might be favoured in higher-mass systems. Thekinematic analysis shows that GS_4891 presents velocity gradients in theionized gas consistent with rotation. The region between GS_4891 and GS_4891_ndoes not present high gas turbulence which, together with the difference in gasmetallicities, suggests that these two systems might be in a pre-merger stage.Finally, GS_4891 hosts an ionized outflow that extends out to r_out=1.2 kpcfrom the nucleus and reaches maximum velocities v_out of approximately 400km/s. Despite entraining an outflowing mass rate of M_out~2Msun/yr, thelow associated mass-loading factor, \eta=0.05, implies that the outflow doesnot have a significant impact on the star-formation activity of the galaxy.