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

TL;DR

This study uses JWST MIRI imaging to reveal hidden star-forming regions, nuclear structures, and extended PAH emission in the luminous IR galaxy VV 114, demonstrating JWST's capability to probe obscured activity in extreme starbursts.

Contribution

First high-resolution JWST MIRI observations of VV 114 uncover detailed nuclear structures, star-forming knots, and diffuse PAH emission, advancing understanding of obscured star formation in luminous IR galaxies.

Findings

VV 114E nucleus resolves into bright NE and SW cores with high IR luminosity.

Approximately 40 star-forming knots identified, with some lacking optical counterparts.

Diffuse PAH emission accounts for half of the 7.7um light, indicating widespread star formation.

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 15um light of VV 114, with the NE and SW cores having IR luminosities, L_ IR (8-1000um) ~ 8+/-0.8x10^10 L_sun and ~ 5+/-0.5x10^10 L_sun, respectively, and IR densities, Sigma_IR >~ 2+/-0.2x10^13 L_sun / kpc^2 and >~ 7+/-0.7x10^12 L_sun / kpc^2, respectively -- in the range of Sigma_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 has AGN-like colors. Approximately 40 star-forming knots with L_IR ~ 0.02-5x10^10 L_sun are identified, 25% of which have no optical counterpart. Finally, diffuse emission accounts for 40-60% of the mid-IR emission. Mostly notably, filamentary Poly-cyclic Aromatic Hydrocarbon (PAH) emission stochastically excited by UV and optical photons accounts for half of the 7.7um 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.