GOALS-JWST: Hidden Star Formation and Extended PAH Emission in the Luminous Infrared Galaxy VV 114

Abstract

James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) images of the luminous infrared (IR) galaxy VV 114 are presented. This redshift ∼0.020 merger has a western component (VV 114W) rich in optical star clusters and an eastern component (VV 114E) hosting a luminous mid-IR nucleus hidden at UV and optical wavelengths by dust lanes. With MIRI, the VV 114E nucleus resolves primarily into bright NE and SW cores separated by 630 pc. This nucleus comprises 45% of the 15 μm light of VV 114, with the NE and SW cores having IR luminosities, L_(IR)(8 − 1000 μm) ∼ 8 ± 0.8 × 10¹⁰ L_⊙ and ∼ 5 ± 0.5 × 10¹⁰ L_⊙, respectively, and IR densities, Σ_(IR) ≳ 2 ± 0.2 × 10¹³ L_⊙ kpc⁻² and ≳ 7 ± 0.7 × 10¹² L_⊙ kpc⁻², respectively—in the range of Σ_(IR) for the Orion star-forming core and the nuclei of Arp 220. The NE core, previously speculated to have an active galactic nucleus (AGN), has starburst-like mid-IR colors. In contrast, the VV 114E SW core has AGN-like colors. Approximately 40 star-forming knots with L_(IR) ∼ 0.02–5 × 10¹⁰ L_⊙ are identified, 28% of which have no optical counterpart. Finally, diffuse emission accounts for 40%–60% of the mid-IR emission. Mostly notably, filamentary polycyclic aromatic hydrocarbon (PAH) emission stochastically excited by UV and optical photons accounts for half of the 7.7 μm light of VV 114. This study illustrates the ability of JWST to detect obscured compact activity and distributed PAH emission in the most extreme starburst galaxies in the local universe.

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