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Arxiv: JWST/MIRI unveils the stellar component of the GN20 dusty galaxy overdensity at z=4.05 Published: 2/28/2024 9:35:28 PM Updated: 6/26/2024 7:39:22 PM

Paper abstract: Despite the importance of the dusty star-forming galaxies (DSFGs) at z>2for understanding the galaxy evolution in the early Universe, their stellardistributions traced by the near-IR emission were spatially unresolved untilthe arrival of the JWST. In this work we present, for the first time, aspatially-resolved morphological analysis of the rest-frame near-IR(~1.1-3.5\mum) emission in DSFGs traced with the JWST/MIRI. In particular, westudy the mature stellar component for the three DSFGs and a Lyman-break galaxy(LBG) present in an overdensity at z=4.05. Moreover, we use MIRI images alongwith UV to (sub)-mm ancillary photometric data to model their SEDs and extracttheir main physical properties. The sub-arcsec resolution MIRI images haverevealed that the stellar component present a wide range of morphologies, fromdisc-like to compact and clump-dominated structures. These near-IR structurescontrast with their UV emission, which is usually diffuse and off-centered. TheSED fitting analysis shows that GN20 dominates the total SFR with a value ~2500M_\odotyr^{-1} while GN20.2b has the highest stellar mass in the sample(M_*~2\times10^{11} M_\odot). The two DSFGs classified as LTGs (GN20and GN20.2a) show high specific SFR (sSFR>30 Gyr^{-1}) placing them above thestar-forming main sequence (SFMS) at z~4 by >0.5 dex while the ETG(i.e.,GN20.2b) is compatible with the high-mass end of the main sequence. Whencomparing with other DSFGs in overdensities at z~2-7 we observe that ourobjects present similar SFRs, depletion times and projected separations.Nevertheless, the effective radii computed for GN20 and GN20.2a are up to twotimes larger than those of isolated galaxies observed in CEERS and ALMA-HUDF atsimilar redshifts. We interpret this difference in size as an effect of rapidgrowth induced by the dense environment.