Shocks, Winds, and a Torus: the Large Binocular Telescope Interferometer (LBTI) Resolves the Active Nucleus of NGC 4151

Abstract We present mid-infrared (MIR) observations of the Seyfert 1 galaxy NGC 4151 using the Large Binocular Telescope Interferometer (LBTI). We took open-loop Fizeau images with 66–104 mas (5.8–9.1 pc) resolution in the N -band (at 8.7 and 10.5 μ m), using the full resolution of the LBTI—equivalent to that of a 28.8 m telescope. These images were complemented by adaptive optics imaging in the LM -bands (3.7 and 4.8 μ m), with 50–62 mas (4.4–5.4 pc) resolution. These images bridge the scales between previous Very Large Telescope Interferometer (VLTI)/MIDI and VLT/VISIR data, delivering Extremely Large Telescope (ELT)–like imaging resolution in the N -band. We resolve a dusty torus (with a diameter of 32 pc and position angle of 125°), and detect dusty clouds within the narrow-line region. Matching the resolution across four bands, we measured spatially resolved SEDs of the central ∼100 pc. Modified blackbody fitting revealed dust temperature and extinction profiles, indicating both heating from the accretion disk and additional shock heating due to the radio jet. The spatial coincidence of ionized emission (e.g., [Fe II ] and [O III ]), extended MIR structures, and radio features further supports the interpretation of shock heating. Comparison with NGC 1068 tests the Unified Model of Active Galactic Nuclei: structures are similar, despite differences in orientation and Eddington ratio. NGC 4151’s torus is smaller than NGC 1068’s following a r ∝ L 0.5 scaling. These ELT-like observations of NGC 4151 and NGC 1068 highlight the need to revise MIR radiative transfer models of AGN to account for jet-related heating.