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Arxiv: MIDIS: JWST/MIRI reveals the Stellar Structure of ALMA-selected Galaxies in the Hubble-UDF at Cosmic Noon Published: 8/31/2023 8:57:04 PM Updated: 4/26/2024 3:50:24 PM

Paper abstract: We present deep James Webb Space Telescope (JWST)/MIRI F560W observations ofa flux-limited, ALMA-selected sample of 28 galaxies at z=0.5-3.6 in the HubbleUltra Deep Field (HUDF). The data from the MIRI Deep Imaging Survey (MIDIS)reveal the stellar structure of the HUDF galaxies at rest-wavelengths of >1micron for the first time. We revise the stellar mass estimates using new JWSTphotometry and find good agreement with pre-JWST analysis; the fewdiscrepancies can be explained by blending issues in the earlierlower-resolution Spitzer data. At z~2.5, the resolved rest-frame near-infrared(1.6 micron) structure of the galaxies is significantly more smooth andcentrally concentrated than seen by HST at rest-frame 450 nm (F160W), witheffective radii of Re(F560W)=1-5 kpc and S\'ersic indices mostly close to anexponential (disk-like) profile (n~1), up to n~5 (excluding AGN). We find anaverage size ratio of Re(F560W)/Re(F160W)~0.7 that decreases with stellar mass.The stellar structure of the ALMA-selected galaxies is indistinguishable from aHUDF reference sample of galaxies with comparable MIRI flux density. Wesupplement our analysis with custom-made, position-dependent, empirical PSFmodels for the F560W observations. The results imply that a smoother stellarstructure is in place in massive gas-rich, star-forming galaxies at CosmicNoon, despite a more clumpy rest-frame optical appearance, placing additionalconstraints on galaxy formation simulations. As a next step,matched-resolution, resolved ALMA observations will be crucial to further linkthe mass- and light-weighted galaxy structures to the dusty interstellarmedium.