Compact Obscured Nuclei. II. Chaotic Central Dust Structures in NGC 4418

Abstract Compact Obscured Nuclei (CONs) are rare types of galactic nuclei obscured by dense, dusty molecular gas. Dusty structures extending beyond hidden CONs produce observable absorption features revealing connections between CONs and their environments. We analyzed central dust features in the CON galaxy NGC 4418, a Luminous Infrared Galaxy using Hubble Space Telescope images. We mapped dust absorption features, calculated optical depths, and derived limits on associated gas masses from color-ratio images. We find NGC 4418 contains complex, three-dimensional spatially resolved dust structures near its CON having τ V ≈ 2–3. This medium is a candidate for the foreground responsible for the deep mid-infrared silicate absorption toward the CON. Our map of the inner dust structures agrees with molecular studies in suggesting the complex structure of the central molecular gas NGC 4418 reflects the ongoing interaction with its companion and the wind from the CON.