GA-NIFS: Co-evolution within a highly star-forming galaxy group at <i>z</i> ∼ 3.7 witnessed by JWST/NIRSpec IFS

Journal article

We present NIRSpec IFS observations of a galaxy group around the massive GS_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, 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. GS_4891 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, GS_4891_n, is also higher by 0.2 dex than at the centre of GS_4891, suggesting that inflows of lower-metallicity gas might be favoured in higher-mass systems. The kinematic analysis shows that GS_4891 presents velocity gradients in the ionised gas consistent with rotation. The region between GS_4891 and GS_4891_n 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, GS_4891 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

Authors: Del Pino, BR; Perna, M; Arribas, S; D’Eugenio, F; Lamperti, I

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: EDP Sciences
• Journal: Astronomy & Astrophysics
• Volume: 684
• Pages: A187-A187
• Publication date: 2024-02-08
• Acceptance date: 2024-01-29
• DOI: 10.1051/0004-6361/202348057
• EISSN: 1432-0746
• ISSN: 0004-6361
• Language: English
• Keywords: Astrophysics; Astronomy; Local Group; Star (game theory); Globular cluster; Group (periodic table); Physics; Dwarf galaxy; Star formation; Galaxy