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

Rogemar A. Riffel, Luis Colina, José Henrique Costa-Souza, Vincenzo Mainieri, Miguel Pereira Santaella, Oli L. Dors, Ismael García-Bernete, Almudena Alonso-Herrero, Anelise Audibert, Enrica Bellocchi, Andrew J. Bunker, Steph Campbell, Françoise Combes, Richard I. Davies, Tanio Díaz-Santos, Fergus R. Donnan, Federico Esposito, Santiago García-Burillo, Begoña García-Lorenzo, Omaira González Martín, Houda Haidar, Erin K. S. Hicks, Sebastian F. Hoenig, Masatoshi Imanishi, Alvaro Labiano, Enrique Lopez-Rodriguez, Christopher Packham, Cristina Ramos Almeida, Dimitra Rigopoulou, David Rosario, Gabriel Luan Souza-Oliveira, Montserrat Villar Martín, Oscar Veenema, Lulu Zhang

First listed 2025-10-02 | Last updated 2025-10-31

Abstract

Active galactic nuclei (AGN), star formation (SF), and galaxy interactions can drive turbulence in the gas of the ISM, which in turn plays a role in the SF 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-ionization gas, in the inner few kpc of both AGN hosts and SF galaxies. We use JWST MIRI/MRS observations of a sample consisting of 54 galaxies at z<0.1. We present fluxes of the H2 S(5)6.9091, [Ar II]6.9853, [FeII]5.3403, and [Ar III]8.9914 lines, along with velocity dispersion from W80. For galaxies with coronal emission, [Mg V]5.6098 is also included. Line ratios are compared to photoionization 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. H2 gas is less turbulent compared to ionized gas, while coronal gas presents higher velocity dispersions. The W80 values for the ionized gas exhibits a decrease 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 W80 and line ratios such as H2 S(5)/[ArII] and [FeII]/[ArII] indicate that the most turbulent gas is associated with shocks, enhancing H2 and [FeII] emissions. We speculate that these shocked gas regions are produced by AGN outflows and jet-cloud interactions in AGN-dominated sources, while in SFGs, they may be created by 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.

Short digest

Using JWST/MIRI MRS cubes for 54 z<0.1 galaxies, the authors map mid-IR lines and W80 to trace ISM turbulence across molecular, low/intermediate-ionization, and coronal gas. AGN show broader lines than SFGs, with radio-strong nuclei having the largest dispersions; H2 is systematically less turbulent than ionized gas, while coronal gas is the most turbulent. Radially, ionized-gas W80 declines from the nucleus to ~0.5–1 kpc then rises again to ~2–3 kpc, whereas H2 widths typically increase with radius. Correlations of W80 with H2 S(5)/[Ar II] and [Fe II]/[Ar II] link the most turbulent regions to shocks, plausibly from AGN outflows or jet–cloud interactions (or stellar winds/mergers in SFGs), indicating shock heating as a viable feedback channel limiting star formation.

Key figures to inspect

• Figure 2 (WISE color–color): Confirms how the five subsamples are defined in IR color space and where radio-strong and Seyfert-like systems sit, grounding later comparisons of W80 among classes.
• Figure 3 (Arp 220 maps): Side-by-side flux and W80 maps for H2 S(5), [Ar II], [Fe II], and [Ar III] illustrate the contrasting radial behavior—ionized-gas turbulence vs the rising H2 widths—and how masking and the chosen nucleus (western peak) affect derived profiles.
• Figure 4 (Nuclear W80 by line): Flux-weighted nuclear dispersions within 0.5″ show the ordering with ionization potential, highlighting that coronal gas has the highest W80 and H2 the lowest, and quantify AGN vs SFG differences with means and scatter.
• Figure 1 (Venn diagram of AGN subsamples): Clarifies overlaps among radio-strong, coronal-line, and other AGN categories, essential for interpreting which populations drive the extreme W80 values.