Dust beyond the torus: Revealing the mid-infrared heart of local Seyfert ESO 428-G14 with JWST/MIRI

TL;DR

This study uses JWST/MIRI imaging to reveal extended polar dust structures within 200 pc of the nucleus in ESO 428-G14, showing their connection to AGN activity and challenging the role of radiation-driven winds.

Contribution

First JWST/MIRI imaging of polar dust in ESO 428-G14, demonstrating the dust's morphology, extent, and heating mechanisms, and questioning the significance of radiation-driven winds.

Findings

Extended MIR emission within 200 pc of the nucleus.

Dust temperature estimated at ~120 K.

Heating primarily from AGN radiation and shocks, not winds.

Abstract

Polar dust has been discovered in a number of local Active Galactic Nuclei (AGN), with radiation-driven torus models predicting a wind to be its main driver. However, little is known about its characteristics, spatial extent, or connection to the larger scale outflows. We present the first JWST/MIRI study aimed at imaging polar dust by zooming onto the centre of ESO 428-G14, part of the Galaxy Activity, Torus, and Outflow Survey (GATOS) survey of local AGN. We detect extended mid-infrared (MIR) emission within 200 pc from the nucleus. This polar structure is co-linear with a radio jet and lies perpendicular to a molecular gas lane that feeds and obscures the nucleus. Its morphology bears a striking resemblance to that of gas ionised by the AGN in the narrow-line region. We demonstrate that part of this spatial correspondence is due to contamination within the JWST filter bands from strong emission lines. Correcting for the contamination, we find the morphology of the dust continuum to be more compact, though still clearly extended out to ~ 100 pc. We estimate the emitting dust has a temperature of ~ 120 K. Using simple models, we find that the heating of small dust grains by the radiation from the central AGN and/or radiative jet-induced shocks is responsible for the extended MIR emission. Radiation-driven dusty winds from the torus is unlikely to be important. This has important implications for scales to which AGN winds can carry dust and dense gas out into their host galaxies.