Impact of active galactic nuclei and nuclear star formation on the ISM turbulence of galaxies: Insights from JWST/MIRI spectroscopy

¹ Centro de Astrobiología (CAB), CSIC-INTA, Ctra. de Ajalvir km 4, Torreón de Ardoz, E-28850 Madrid, Spain
² Departamento de Física, CCNE, Universidade Federal de Santa Maria, Av. Roraima 1000, 97105-900 Santa Maria, RS, Brazil
³ European Southern Observatory, Karl-Schwarzschild-Strasse 2, Garching bei München, Germany
⁴ Instituto de Física Fundamental, CSIC, Calle Serrano 123, E-28006 Madrid, Spain
⁵ Universidade do Vale do Paraíba, Av. Shishima Hifumi, 2911, Cep 12244-000 São José dos Campos, SP, Brazil
⁶ Centro de Astrobiología (CAB), CSIC-INTA, Camino Bajo del Castillo s/n, E-28692 Villanueva de la Cañada, Madrid, Spain
⁷ Instituto de Astrofísica de Canarias, Calle Vía Láctea, s/n, E-38205 La Laguna, Tenerife, Spain
⁸ Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
⁹ Departmento de Física de la Tierra y Astrofísica, Fac. de CC Físicas, Universidad Complutense de Madrid, E-28040 Madrid, Spain
¹⁰ Instituto de Física de Partículas y del Cosmos IPARCOS, Fac. CC Físicas, Universidad Complutense de Madrid, E-28040 Madrid, Spain
¹¹ Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH UK
¹² School of Mathematics, Statistics, and Physics, Newcastle University, Newcastle upon Tyne, NE1 7RU UK
¹³ Observatoire de Paris, LUX, PSL University, Sorbonne Université, CNRS, F-75014 Paris, France
¹⁴ Collège de France, 11 Place Marcelin Berthelot, 75231 Paris, France
¹⁵ Max-Planck-Institut für Extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
¹⁶ Institute of Astrophysics, Foundation for Research and TechnologyHellas, 71110 Heraklion, Greece
¹⁷ School of Sciences, European University Cyprus, Diogenes Street, Engomi, 1516 Nicosia, Cyprus
¹⁸ Center for Astrophysics & Space Sciences, Department of Physics, University of California San Diego, 9500 Gilman Drive, San Diego, CA, 92093 USA
¹⁹ Observatorio de Madrid, OAN-IGN, Alfonso XII, 3, E-28014 Madrid, Spain
²⁰ Instituto de Radioastronomía y Astrofísica (IRyA), Universidad Nacional Autónoma de México, Antigua Carretera a Pátzcuaro #8701, Ex-Hda. San José de la Huerta, C.P. 58089 Morelia, Michoacán, Mexico
²¹ Department of Physics & Astronomy, University of Alaska Anchorage, Anchorage, AK, 99508-4664 USA
²² Department of Physics, University of Alaska, Fairbanks, Alaska, 99775-5920 USA
²³ Department of Physics & Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX, 78249 USA
²⁴ School of Physics & Astronomy, University of Southampton, Southampton, SO17 1BJ UK
²⁵ National Astronomical Observatory of Japan, National Institutes of Natural Sciences (NINS), 2-21-1 Osawa, Mitaka, Tokyo, 181-8588 Japan
²⁶ Department of Astronomy, School of Science, Graduate University for Advanced Studies (SOKENDAI), Mitaka, Tokyo, 181-8588 Japan
²⁷ Telespazio UK for the European Space Agency (ESA), ESAC, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Spain
²⁸ Department of Physics & Astronomy, University of South Carolina, Columbia, SC, 29208 USA
²⁹ Kavli Institute for Particle Astrophysics & Cosmology (KIPAC), Stanford University, Stanford, CA, 94305 USA
³⁰ Department of Physics, University of Oxford, Keble Road, Oxford, OX1 3RH UK
³¹ School of Sciences, European University Cyprus, Diogenes street, Engomi, 1516 Nicosia, Cyprus

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Received: 7 August 2025
Accepted: 31 October 2025

Abstract

Active galactic nuclei (AGNs), star formation (SF), and galaxy interactions can drive turbulence in the gas of the interstellar medium (ISM), which, in turn, plays a role in SF taking place within galaxies. The impact on molecular gas is of particular importance, as it serves as the primary fuel for SF. Our goal is to investigate the origin of turbulence and the emission of molecular gas, as well as low-and-intermediate-ionisation gas, in the inner few kpc of both AGN hosts and star-forming galaxies (SFGs). We used archival JWST MIRI/MRS observations of a sample consisting of 54 galaxies at z < 0.1. We present flux measurements for the H₂ S(5)λ6.9091 μm, [ArII]λ6.9853 μm, [FeII]λ5.3403 μm, and [ArIII]λ8.9914 μm emission lines along with velocity dispersion estimated by the W₈₀ parameter. For galaxies with coronal line emission, we included measurements of the [MgV]λ5.6098 μm line. We compared the line ratios to photoionisation and shock models to explore the origin of the gas emission. AGNs exhibit broader emission lines than SFGs, with the largest velocity dispersions observed in radio-strong (RS) AGNs. The H₂ gas is less turbulent compared to ionised gas, while coronal gas presents higher velocity dispersions. The W₈₀ values for the ionised gas show a decrease when going from the nucleus out to radii of approximately 0.5–1 kpc, followed by an outward increase up to 2–3 kpc. In contrast, the H₂ line widths generally display increasing profiles with distance from the center. Correlations between the W₈₀ parameter and line ratios such as H₂S(5)/[Ar II] and [Fe II]/[Ar II] indicate that the most turbulent gas is associated with shocks, enhancing H₂ and [Fe II] emissions. Based on the observed line ratios and velocity dispersions, the [FeII] emission is consistent with predictions of fast shock models, while the H₂ emission is likely associated with molecules formed in the post-shock region. We speculate that these shocked gas regions are produced by AGN outflows and jet-cloud interactions in AGN-dominated sources; whereas in SFGs, they might be created through stellar winds and mergers. This shock-induced gas heating may be an important mechanism of AGN (or stellar) feedback, preventing the gas from cooling and forming new stars.