Shocked, Heated, and Now Resolved: H$_2$ excitation in the low-luminosity AGN at M58 core with JWST

I. E. López, E. Bertola, V. Reynaldi, P. Ogle, R. D. Baldi, M. Brusa, S. García-Burillo, B. Sebastian, M. V. Zanchettin, G. Cresci, J. A. Fernández-Ontiveros, A. Marconi, R. M. Rich, T. M. Rodriguez

First listed 2025-09-29 | Last updated 2025-10-28

Abstract

We present JWST NIRSpec and MIRI MRS observations of the central kiloparsec of M58 (NGC 4579), a nearby LINER galaxy hosting a low-luminosity AGN (LLAGN; $L_\mathrm{bol} \sim 10^{42}$ erg s$^{-1}$) with a low-power jet. These data provide an unprecedented view of the warm molecular gas phase and reveal clear signatures of feedback. We detect 44 H$_2$ lines, including bright pure rotational lines (S(1)-S(18)) and rovibrational lines up to $ν=2$, probing a wide range of excitation conditions. Excitation diagrams show that rotational lines follow a power-law temperature distribution with an exponential cutoff, consistent with heating by low-velocity shocks. H$_2$ rovibrational lines deviate from thermal models primarily because of sub-thermal excitation at low density. Additionally, there may be a 10% contribution powered by AGN X-ray photons in the nucleus. The dust lanes associated with the spiral inflow appear dynamically undisturbed but show signs of shock heating, while the inner $\sim$200 pc exhibits turbulent kinematics produced by outflowing molecular gas. These results reveal the subtle yet measurable impact of LLAGN feedback on the interstellar medium, demonstrating that even weak, vertically oriented jets and low radiative accretion rates can perturb molecular gas and regulate nuclear reservoirs. This study highlights JWST's transformative ability to uncover hidden modes of AGN feedback.

Short digest

JWST/NIRSpec+MIRI IFU mapping of M58 (NGC 4579) resolves the warm H2 across the central kiloparsec of a LINER LLAGN with a low-power jet. The team detects 44 H2 lines—rotational S(1)–S(18) and rovibrational up to v=2—whose excitation follows a power-law temperature distribution with an exponential cutoff, pointing to low-velocity shock heating; the rovibrational lines are sub-thermal, with a minor (~10%) nuclear X-ray contribution. Dust-lane gas tied to the spiral inflow looks dynamically calm yet shock-heated, while the inner ~200 pc shows turbulent, outflowing molecular kinematics. Result: even weak, vertically oriented jets can measurably perturb nuclear molecular reservoirs, a subtle LLAGN feedback mode now cleanly exposed by JWST.

Key figures to inspect

• Fig. 1: Compare H2 (F212N, S(1)/S(9)) with PAH and stellar maps plus LOFAR/VLA/MERLIN contours to see how warm H2 aligns with the dust lanes and where shocks (NE/SW) sit relative to the radio jet.
• Fig. 2: Contrast nuclear vs circumnuclear spectra to gauge the enhancement of H2 rovibrational lines, presence of high-ionization lines, and the dual silicate features, separating jet/AGN-heated gas from SF-dominated regions.
• Fig. 3: Inspect H2, [Ar II], and [Ne V] moment maps for spatial/kinematic decoupling and orientation versus the jet and galaxy major axis; note where high-ionization gas peaks relative to the AGN core.
• Fig. 4: Use the H2 1–0 S(1) and S(9) channel maps across −500…+500 km s−1 to isolate rotating dust-lane emission versus the NE forward-shock feature (−500 to +200 km s−1) and the misalignment that implies the jet passes outside the disk plane.