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

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 $μ$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 $μ$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.