MIRACLE

I. Unveiling the multi-phase, multi-scale physical properties of the active galaxy NGC 424 with MIRI, MUSE, and ALMA

¹ Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Via G. Sansone 1, I-50019 Sesto Fiorentino, Firenze, Italy
² INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
³ University of Trento, Via Sommarive 14, Trento, I-38123, Italy
⁴ Scuola Normale Superiore, Piazza dei Cavalieri 7, Pisa I-56126, Italy
⁵ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Plaza San Juan 1, 44001 Teruel, Spain
⁶ Istituto di Astrofisica e Planetologia Spaziali (INAF-IAPS), Via Fosso del Cavaliere 100, 00133 Roma, Italy
⁷ Instituto de Radioastronomía y Astrofísica, UNAM, Campus Morelia, A.P. 3-72, C.P. 58089, Mexico
⁸ ESO, Karl-Schwarzschild-Str 2, D-85748 Garching bei München, Germany
⁹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
¹⁰ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
¹¹ Institute for Physics, Laboratory for Galaxy Evolution and Spectral Modelling, Ecole Polytechnique Federale de Lausanne, Observatoire de Sauverny, Chemin Pegasi 51, CH-1290 Versoix, Switzerland
¹² INAF, Osservatorio Astronomico di Trieste, Via Tiepolo 11, I-34131 Trieste, Italy
¹³ AURA for ESA, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁴ Departamento de Física, Universidad Técnica Federico Santa María, Vicuña Mackenna 3939, San Joaquín, Santiago de Chile, Chile
¹⁵ IFPU – Institute for Fundamental Physics of the Universe, via Beirut 2, I-34151 Trieste, Italy
¹⁶ Max-Planck-Institut für extraterrestrische Physik (MPE), Gießenbachstraße 1, 85748 Garching, Germany
¹⁷ Observatorio Astronómico Nacional, C/ Alfonso XII 3, E-28014 Madrid, Spain
¹⁸ Dipartimento di Fisica e Astronomia, Alma Mater Studiorum, Università degli Studi di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
¹⁹ INAF–Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy
²⁰ Department of Physics, University of Arkansas, 226 Physics Building, 825 West Dickson Street, Fayetteville, AR 72701, USA

^⋆ Corresponding author cosimo.marconcini@unifi.it

Received: 27 March 2025
Accepted: 17 July 2025

Abstract

We present an analysis of the multi-phase gas properties in the Seyfert II galaxy NGC 424, using spatially resolved spectroscopic data from JWST/MIRI, part of the Mid-InfraRed Activity of Circumnuclear Line Emission (MIRACLE) programme, as well as VLT/MUSE and ALMA. We traced the properties of the multi-phase medium, from cold and warm molecular gas to hot ionised gas, using emission lines such as CO (2-1), H₂S(1), [O III]λ5007, [Ne III]15.55μm, and [Ne V]14.32μm. These lines reveal the intricate interplay between the different gas phases within the circumnuclear region, spanning a maximum scale of 7 × 7 kpc² and a spatial resolution of 110 pc, with MUSE and ALMA, respectively. Exploiting the multi-wavelength and multi-scale observations of gas emission, we modelled the galaxy disc rotation curve from scales of a few parsec up to ∼5 kpc from the nucleus and inferred a dynamical mass of M_dyn = (1.09 ± 0.08) × 10¹⁰ M_⊙ with a disc scale radius of R_D = (0.48 ± 0.02) kpc. We detected a compact ionised outflow with velocities up to 10³ km s⁻¹, traced by the [O III], [Ne III], and [Ne V] transitions, with no evidence of cold or warm molecular outflows. We suggest that the ionised outflow might be able to inject a significant amount of energy into the circumnuclear region, potentially hindering the formation of a molecular wind, as the molecular gas is observed to be denser and less diffuse. The combined multi-band observations also reveal, mainly in the ionised and cold molecular gas phases, a strong enhancement of the gas velocity dispersion directed along the galaxy minor axis, perpendicular to the high-velocity ionised outflow, and extending up to 1 kpc from the nucleus. Our findings suggest that the outflow might play a key role in such an enhancement by injecting energy into the host disc and perturbing the ambient material.