GATOS XI : Excess dust heating in the Narrow Line Regions of nearby AGN revealed with JWST/MIRI

Houda Haidar, David J. Rosario, Ismael García-Bernete, Almudena Alonso-Herrero, Anelise Audibert, Steph Campbell, Chris M. Harrison, Tiago Costa, Laura Hermosa Muñoz, Françoise Combes, Dimitra Rigopoulou, Claudio Ricci, Cristina Ramos Almeida, Enrica Bellocchi, Peter Boorman, Andrew Bunker, Richard Davies, Daniel Delaney, Tanio Díaz Santos, Federico Esposito, Victoria A. Fawcett, Poshak Gandhi, Santiago García-Burillo, Omaira González-Martín, Erin K. S. Hicks, Sebastian F. Hönig, Alvaro Labiano, Nancy A. Levenson, Enrique Lopez-Rodriguez, Chris Packham, Miguel Pereira-Santaella, Rogemar A. Riffel, Alberto Rodríguez Ardila, John Schneider, T. Taro Shimizu, Marko Stalevski, Montserrat Villar Martín, Martin Ward, Lulu Zhang, Gillian Leeds, Fergus R. Donnan

First listed 2026-01-06 | Last updated 2026-01-06

Abstract

We present JWST/MIRI imaging of eight nearby Active Galactic Nuclei (AGN) from the GATOS survey to investigate the physical conditions of extended dust in their narrow line regions (NLRs). In four galaxies (ESO 428-G14, NGC 4388, NGC 3081, and NGC 5728), we detect spatially resolved dust structures extending ~100-200 pc along the NLR. In these systems, we find a strong link between the morphology of the dust, the radio ejecta, and the coronal [Si VI] emission, implying that dust carries imprints of the processes shaping the NLR. Using spatially resolved spectral energy distributions, we show that dust in the NLR has systematically steeper slopes than star forming clumps. This dust emits at temperatures in the range 150 - 220 K, at a distance of ~150 pc from the nucleus. Using simple models, we show that, even under optimistic assumptions of grain size and AGN luminosity, the excess MIR emission cannot be explained by AGN illumination alone. We interpret this excess heating as in-situ. We show that shocks with velocities of $v_{\rm shock} \sim 200- 400 \, \rm km/s$ in dense gas can close this gap, and in some cases even account for the total observed emission. This, combined with multiple lines of evidence for shocks in these regions, supports a scenario in which shocks not only coexist with dust but may be playing a key role in heating it. Our findings reveal shocks may be an important and previously overlooked driver of extended dust emission in the central hundreds of parsecs in AGN.

Short digest

JWST/MIRI imaging of eight nearby GATOS AGN isolates extended NLR dust and tests its heating budget. Four nuclei—ESO 428‑G14, NGC 4388, NGC 3081, and NGC 5728—show 100–200 pc dust structures whose morphology tracks the radio ejecta and coronal [Si VI]. Spatially resolved SEDs reveal steeper MIR slopes than in star‑forming clumps and blackbody fits yield 150–220 K at ~150 pc from the nucleus. Simple AGN-illumination models underpredict the flux, while shocks with v_shock ≈ 200–400 km/s in dense gas can close the gap, elevating shocks as a key driver of extended MIR dust emission in AGN centers.

Key figures to inspect

• Fig. 1: PSF‑subtracted, line‑decontaminated F1000W maps for ESO 428‑G14, NGC 4388, NGC 3081, NGC 5728—inspect 100–200 pc dust features aligned with [Si VI] and radio contours; note arrows marking [Fe II]‑enhanced shock zones.
• Fig. 2: Companion F1000W panels for NGC 7172, NGC 2992, NGC 3227, NGC 5135—compare weaker/absent extended dust to the four detections to gauge how NLR geometry or activity level modulates dust visibility.
• Fig. 3: Five‑band MIRI SEDs (normalized by F1500W)—verify that NLR ROIs have systematically steeper MIR slopes than star‑forming clumps across galaxies, establishing a distinct heating mechanism.
• Fig. 4: Monte‑Carlo blackbody fits at 150 pc in shock‑dominated apertures—read off 150–220 K temperatures and confidence ranges, the key inputs showing why AGN illumination alone is insufficient.