A Multi-Wavelength Investigation of Dust and Stellar Mass Distributions in Galaxies: Insights from High-Resolution JWST Imaging

Abstract: We study the morphological properties of mid-infrared selected galaxies at $1.0<z<1.7$ in the SMACS J0723.3-7327 cluster field, to investigate the mechanisms of galaxy mass assembly and structural formation at cosmic noon. We develop a new algorithm to decompose the dust and stellar components of individual galaxies by utilizing high-resolution images in the MIRI F770W and NIRCam F200W bands. Our analysis reveals that a significant number of galaxies with stellar masses between ${\rm 10<sup>{9.5}&lt;M_*/M_\odot&lt;10<sup>{10.5}}$ exhibit dust cores that are relatively more compact compared to their stellar cores. Specifically, within this mass range, the non-parametric method indicates that the dust cores are, on average, 1.23 ($\pm0.05$) times more compact than the stellar cores, when evaluated with flux concentration of the two components within a fixed radius. Similarly, the parametric method yields an average compactness ratio of 1.27 ($\pm0.06$). Notably, the most massive galaxy ($\rm{M_* \sim 10<sup>{10.9}\,M_\odot}$) in our sample demonstrates a comparable level of compactness between its stellar core and dust, with a dust-to-stellar ratio of 0.86 (0.89) as derived from non-parametric (parametric) method. The observed compactness of the dust component is potentially attributed to the presence of a (rapidly growing) massive bulge, in some cases associated with elevated star formation. Expanding the sample size through a joint analysis of multiple Cycle~1 deep-imaging programs can help to confirm the inferred picture. Our pilot study highlights that MIRI offers an efficient approach to studying the structural formation of galaxies from cosmic noon to the modern universe.