The Obscured Nucleus and Shocked Environment of VV 114E Revealed by JWST/MIRI Spectroscopy

TL;DR

This study uses JWST/MIRI spectroscopy to analyze the heavily obscured nucleus of VV 114E, revealing a compact obscured nucleus with shock features and star-forming regions, and providing insights into hidden SMBH growth.

Contribution

First detailed mid-infrared spectroscopic analysis of VV 114E's obscured nucleus and environment using JWST, identifying shock fronts and characterizing obscuration levels.

Findings

The NE nucleus is highly obscured with a dust-enshrouded continuum.

PAH ratios indicate star formation rather than AGN activity.

Shock front detected with PAH destruction evidence.

Abstract

Compact Obscured Nuclei (CONs) potentially hide extreme supermassive black hole (SMBH) growth behind large column densities of gas/dust. We present a spectroscopic analysis of the heavily obscured nucleus and the surrounding environment of the eastern region of the nearby ($z = 0.02007$) interacting galaxy VV 114 with the JWST Mid-InfraRed Instrument (MIRI). We model the spectrum from 4.9 - 28 $\mu$m to extract Polycyclic Aromatic Hydrocarbon (PAH) emission and the underlying obscured continuum. We find that the NE nucleus (A) is highly obscured where the low PAH equivalent width (EW) ratio, EW(12.7)/EW(11.3), reveals a dust enshrouded continuum source. This is confirmed by decomposing the continuum into nuclear and star-forming where the nuclear component is found to be typical of CONs. The 11.3/6.2 PAH flux ratio is consistent with originating in star-forming regions rather than typical AGN. The second nucleus (B) is much less obscured, with PAH flux ratios also typical of star-forming regions. We do not detect any high ionisation lines such as [Ne V] or [Ne VI] which suggests that if an AGN is present it must be highly obscured. Additionally, we detect a shock front south of the secondary nucleus (B) in the [Fe II] (5.34 $\mu$m) line and in warm molecular hydrogen. The 6.2 PAH emission does not spatially coincide with the low-J transitions of H$_2$ but rather appears strong at the shock front which may suggest destruction of the ionised PAHs in the post-shock gas behind the shock front.