Early JWST Imaging Reveals Strong Optical and NIR Color Gradients in Galaxies at z similar to 2 Driven Mostly by Dust

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Recent studies have shown that galaxies at cosmic noon are redder in the center and bluer in the outskirts, mirroring results in the local universe. These color gradients could be caused by gradients in either the stellar age or dust opacity; however, distinguishing between these two causes is impossible with rest-frame optical photometry alone. Here we investigate the underlying causes of the gradients from spatially resolved rest-frame U - V versus V - J color-color diagrams measured from early observations with the James Webb Space Telescope. We use 1-4 mu m NIRCam photometry from the CEERS survey of a sample of 54 galaxies with log M-* /M-circle dot > 10 at redshifts 1.7 < z < 2.3 selected from the 3D-HST catalog. We model the light profiles in the F115W, F200W, and F356W NIRCam bands using imcascade, a Bayesian implementation of the multi-Gaussian expansion technique that flexibly represents galaxy profiles using a series of Gaussians. We construct resolved rest-frame U - V and V - J color profiles. The majority of star-forming galaxies have negative gradients (i.e., redder in the center, bluer in the outskirts) in both U - V and V - J colors consistent with radially decreasing dust attenuation. A smaller population (roughly 15%) of star-forming galaxies have positive U - V but negative V - J gradients implying centrally concentrated star formation. For quiescent galaxies, we find a diversity of UVJ color profiles, with roughly one-third showing star formation in their center. This study showcases the potential of JWST to study the resolved stellar populations of galaxies at cosmic noon.

Original languageEnglish
Article number37
JournalAstrophysical Journal Letters
Issue number2
Number of pages8
Publication statusPublished - 1 Dec 2022

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