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
TL;DR
The study addresses how LLAGN govern their ISM and accretion physics by measuring infrared emission lines with unprecedented spatial resolution. It uses JWST NIRSpec and MIRI/MRS to obtain nuclear spectra for eight LLAGN (seven ReveaLLAGN targets plus Cen A), covering 1.66–28.9 μm. Key results include detection of high-ionization lines at very faint levels, a transition to UV-deficient SEDs near $\log(L_{\rm bol}/L_{\rm Edd}) \approx -3.5$, elevated $H_2$ rotational temperatures (~500 K higher) relative to higher-luminosity AGN and star-forming galaxies, and $H_2(0-0)S(3)/PAH_{11.3\mu m}$ ratios consistent with the AGN population. The data also reveal possible roles for outflows, jets, and XDRs in shaping the LLAGN ISM and provide the first JWST-based IR emission-line census of LLAGN nuclear regions.
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.