ReveaLLAGN 1: JWST Emission-Line Spectra Reveal Low-Luminosity AGN with UV-Deficient SEDs and Warm Molecular Gas

Kameron Goold, Anil Seth, Mallory Molina, David Ohlson, Nischal Acharya, Torsten Böker, Antoine Dumont, Michael Eracleous, Anja Feldmeier-Krause, Juan Antonio Fernández-Ontiveros, Elena Gallo, Andy D. Goulding, Kayhan Gültekin, Luis C. Ho, Nadine Neumayer, Richard M. Plotkin, Almudena Prieto, Jessie C. Runnoe, Shobita Satyapal, Glenn van de Ven, Jonelle L. Walsh, Feng Yuan, Nora Lützgendorf

First listed 2026-01-23 | Last updated 2026-02-12

Abstract

We present near- and mid-infrared spectra of eight Low-Luminosity Active Galactic Nuclei (LLAGN), spanning nearly four orders of magnitude in black hole mass and Eddington ratio, obtained with JWST/NIRSpec and MIRI as part of the ReveaLLAGN program along with identical archival data of Cen A. The high spatial resolution of JWST cleanly separates AGN emission from host-galaxy contamination, enabling detections of high-ionization potential lines more than an order of magnitude fainter than previously measured. Emission-line diagnostics reveal a transition at log($L_{bol}/L_{Edd}$) ~ -3.5, where the spectral energy distribution becomes increasingly deficient in ultraviolet photons. We find that rotational H$_2$ excitation temperatures are elevated (~500 K higher) compared to both higher-luminosity AGN and star-forming galaxies, while the H$_2$(0-0)S(3)/PAH$_{11.3 μm}$ ratios are consistent with those observed in the AGN population. We discuss the possible roles of outflows, jets, and X-ray dominated regions in shaping the interstellar medium surrounding LLAGN. Silicate emission at ~10 $μ$m, localized to the nuclear region, is detected in most ReveaLLAGN targets. This dataset offers the first comprehensive JWST-based characterization of infrared emission lines in the nuclear regions of LLAGN.

Short digest

JWST/NIRSpec and MIRI IFU spectra for eight nearby LLAGN (plus Cen A) cleanly isolate the nuclei, enabling detections of high–ionization lines more than an order of magnitude fainter than before. Emission-line diagnostics show a transition near log(Lbol/LEdd) ≈ −3.5 where the SED becomes increasingly UV-deficient, while [Ne V] 14 μm and [O IV] 26 μm remain tightly correlated down to the lowest luminosities. The nuclear molecular gas is unusually warm, with rotational H2 temperatures ≈500 K higher than in luminous AGN and star-forming galaxies, and most targets show compact 10 μm silicate emission. High-S/N forbidden-line profiles also reveal IP-dependent kinematics, including double-peaked structure in M87 with a peak dominance change around 23 eV, underscoring feedback-shaped nuclear environments in LLAGN.

Key figures to inspect

• Figure 1: Scan the nuclear spectra (normalized to MIRI/MRS ch.1) to inventory high-IP lines per target and verify that NGC 4395’s line roster and continuum features are captured within the NIRSpec/MIRI coverage gaps.
• Figure 2: Inspect the forbidden-line profiles across IP to see the kinematic stratification; in M87 note the systematic double peaks and the switch in dominant peak near IP ≈23 eV, and compare widths/offsets (≈+280/−450 km/s) across the sample.
• Figure 3: Check nuclear/annular flux ratios against the point-source expectation to confirm the emission is unresolved and minimally host-contaminated, and look for any outliers versus Eddington ratio.
• Figure 4: Use the [Ne V] 14 μm vs [O IV] 26 μm plane to verify the extension of the correlation to very low luminosities (with M94 as the faint end) and to benchmark ReveaLLAGN nuclei against legacy samples.