ReveaLLAGN Program: JWST LLAGN Survey

• ReveaLLAGN is a JWST-based spectral survey that maps the nuclear regions of low-luminosity active galactic nuclei to isolate intrinsic AGN signals from host galaxy light.
• It employs NIRSpec and MIRI IFU spectroscopy to achieve high spatial and spectral resolution, providing detailed diagnostics of accretion modes, kinematics, and chemical conditions on parsec scales.
• The program establishes empirical spectral templates to delineate transitions from UV-bright to UV-deficient regimes, deepening our understanding of AGN feedback and low-Eddington accretion physics.

The ReveaLLAGN (Revealing Low-Luminosity Active Galactic Nuclei) Program is a JWST-based spectral survey targeting the nuclear regions of nearby low-luminosity AGN (LLAGN). Designed as a Cycle-1 JWST treasury program, ReveaLLAGN combines near-infrared and mid-infrared integral field unit (IFU) spectroscopy to systematically map the physical, kinematic, and chemical conditions of LLAGN on parsec scales. By employing the NIRSpec and MIRI instruments, ReveaLLAGN achieves high spatial and spectral resolution sufficient to isolate AGN emission from host-galaxy contamination, facilitating the detection of key coronal lines, molecular hydrogen features, and dust signatures essential for diagnosing accretion mode, nuclear feedback, and ISM energetics in the low-Eddington-ratio regime (Goold et al., 2023, Goold et al., 23 Jan 2026).

1. Scientific Motivation and Objectives

The primary goals of ReveaLLAGN are twofold: (1) to construct empirical spectral templates of LLAGN unobscured by host-galaxy light, enabling robust identification of faint or hidden AGN in both the local and high-redshift universe; and (2) to exploit the spatial and spectral capabilities of JWST to probe accretion, ionization, and feedback processes in low-power AGN with unprecedented detail. LLAGN dominate the local AGN demographic but are characteristically faint compared to Seyfert nuclei, typically harbor radiatively inefficient accretion flows (RIAFs), and often lack strong UV signatures, broad-line regions, or a classical torus structure. ReveaLLAGN addresses observational and theoretical questions regarding how LLAGN differ from classical AGN in their ionizing SEDs, feedback mechanisms, and ISM impact (Goold et al., 2023, Goold et al., 23 Jan 2026).

A key motivation is to empirically establish the transition from UV-bright, thin-disk accretion to RIAF- or jet-dominated modes, as reflected in both emission line diagnostics and continuum properties. The program seeks to quantify outflows, warm molecular gas properties, and nuclear dust features across a representative sample, anchored in a homogeneous multiwavelength context.

2. Sample Selection and Parameter Space

The principal sample comprises seven well-studied, nearby LLAGN plus archival data on the prototypical radio galaxy Cen A, collectively spanning a wide range in black hole mass ($\log M_{\rm BH}/M_\odot \approx 5.6$–$9.8$) and Eddington ratio ($\log (L_{\rm bol}/L_{\rm Edd}) \approx -6.2$ to $-2.7$) (Goold et al., 23 Jan 2026). Nearly four orders of magnitude in both $M_{\rm BH}$ and $L_{\rm bol}/L_{\rm Edd}$ are covered, with distances ranging from 3.7 to 19.4 Mpc. Most targets possess LINER-type optical spectra, granting leverage over the low-accretion-rate parameter space that dominates the local AGN population.

Bolometric luminosities $L_{\rm bol}$ are uniformly derived from absorption-corrected $2–10$ keV X-ray luminosities using the Duras et al. (2020) correction, and Eddington ratios employ the standard prescription

$$L_{\rm Edd} = 1.26 \times 10^{38}\, \Bigl(\frac{M_{\rm BH}}{M_\odot}\Bigr)\,\mathrm{erg\,s^{-1}}.$$

This sample strategy enables ReveaLLAGN to probe the predicted threshold at $\log(L_{\rm bol}/L_{\rm Edd}) \sim -3.5$ where AGN SEDs transition from UV-bright (“big blue bump”) to UV-deficient regimes (Goold et al., 23 Jan 2026).

3. JWST Observational Methodology and Data Reduction

ReveaLLAGN employs both JWST/NIRSpec IFU (R $\sim 2700$, $1.66$–$5.27~\mu$m) and JWST/MIRI MRS (R $\sim 3000$–$4600$, $4.9$–$28.1~\mu$m) for all targets. MIRI MRS divides the spectral domain into four channels, each with three sub-bands and up to 6.6″×7.7″ fields of view. Exposure strategies involve four-point dithering per observation with dedicated off-source backgrounds (Goold et al., 2023, Goold et al., 23 Jan 2026).

Raw data are processed through JWST pipeline stages (up to v1.15.x), with detector calibrations, stray light/fringe corrections, 3D cube reconstruction, and background subtraction. For MIRI, master-backgrounds are subtracted at the cube-building stage, while NIRSpec data are corrected for under-sampling “wiggles” using the WICKED Fourier-based tool.

Nuclear spectra are extracted using wavelength-dependent apertures enclosing 75% of encircled energy, with sky subtraction from adjacent annuli. Absolute wavelength calibration achieves $\Delta v \approx 10$–$30~\mathrm{km\,s}^{-1}$, and photometric accuracy is better than 10% (channels 1–3, slightly lower in channel 4).

4. Spectral Diagnostics: Emission Lines, Kinematics, and Line Ratios

High-fidelity nuclear spectra allow isolation of AGN continuum and forbidden line emission on parsec scales. Emission-line analysis utilizes multi-Gaussian decomposition, correcting for instrumental broadening. Key diagnostics include:

• Detection of high-ionization-potential coronal lines ([Ne V] $14.322~\mu$m, $24.318~\mu$m; [O IV] $25.890~\mu$m, [Ne VI] $7.65~\mu$m) at luminosities more than an order of magnitude fainter than previous surveys.
• Measurement of line widths (FWHM) and velocities, showing that for LLAGN line widths increase strongly with ionization potential (reaching $>1000~\mathrm{km\,s}^{-1}$ for $\mathrm{IP} \gtrsim 50$ eV), with lines significantly blue-shifted—interpreted as evidence of jet-driven or RIAF-driven nuclear outflows. Lower-ionization lines remain narrower and near systemic velocity.
• Luminosity and ratio correlations: The [Ne V]/[Ne III] and [Ne V]/[Ne II] ratios in LLAGN are suppressed relative to classical Seyferts at the same X-ray luminosity, consistent with strong UV deficiency in the ionizing SED below the $\log(L_{\rm bol}/L_{\rm Edd}) \sim -3.5$ threshold discovered empirically in the ReveaLLAGN sample (Goold et al., 23 Jan 2026).
• In select targets (Sombrero, NGC 1052, M87), the emergence of blue wings and broadened high-IP lines argues for multiphase, AGN-driven feedback extending to several tens of parsecs.

5. Molecular Gas and Dust Diagnostics

ReveaLLAGN characterizes the properties of warm molecular gas through pure rotational H$_2$ emission lines (0–0 S(1) through S(8)), as well as nuclear dust via mid-infrared silicate features.

• H$_2$ rotational excitation temperatures in LLAGN are elevated by $\sim500$ K compared to higher-luminosity AGN and star-forming galaxies for $J > 3$ levels, indicating non-PDR heating mechanisms such as shocks or X-ray–dominated regions (XDRs).
• The H$_2$(0–0)S(3)/PAH$_{11.3~\mu\mathrm{m}}$ ratio serves as a diagnostic, with values in LLAGN consistent with AGN-driven or shock/XDR heating rather than pure star formation. Median values $\sim0.044$, with the highest ratio $0.64$ in NGC 4395, further distinguish the sample from star-forming templates (Goold et al., 23 Jan 2026).
• Broad silicate emission at $10~\mu$m is detected in most nuclei (except M87 and Cen A, where it is absent or appears in absorption). The strength is quantified as $$S_{\rm sil} = -\ln (f(\lambda_{\rm peak})/f_c(\lambda_{\rm peak}))$$, and morphology studies localize the emission to scales $\lesssim 0.4''$ ($\lesssim 30$ pc), potentially arising from clumpy torus remnants, NLR dust, or compact dusty filaments.

6. Feedback Phenomena: Outflows, Jets, and Ionization Structure

ReveaLLAGN reveals that even the faintest LLAGN show signatures of AGN mechanical feedback. Multiple findings support this:

• IP-stratified line broadening, blue-shifted high-IP lines, and pronounced velocity asymmetries align spatially with known radio jets or optical outflows.
• The compactness of coronal emission (intrinsic FWHM $<0.1''$, i.e, $\lesssim10$ pc) combined with resolved lower-ionization gas (10–30 pc) is consistent with stratified nuclear outflows.
• Absence of PAH-blending or strong nuclear star formation contamination in the emission line spectra further supports the AGN origin of these features.
• Elevated molecular gas temperatures, high H$_2$/PAH ratios, and the $L_{\rm H_2}/L_{2-10\,\rm keV}<10^{-2}$ criterion are compatible with X-ray heating and jet- or wind-driven shock excitation.

A plausible implication is that, in the $\log(L_{\rm bol}/L_{\rm Edd}) \lesssim -3.5$ regime, even radiatively inefficient AGN can drive significant multiphase feedback into their circumnuclear ISM, scaling down in energetics but remaining structurally analogous to higher-luminosity AGN (Goold et al., 2023, Goold et al., 23 Jan 2026).

7. Implications for AGN Physics and Future Directions

ReveaLLAGN provides the first comprehensive, JWST-based, empirical dataset mapping low-power AGN accretion and feedback processes at parsec resolution. Key findings and implications include:

• Empirical identification of a break in UV photon output at $\log(L_{\rm bol}/L_{\rm Edd})\sim -3.5$, interpreted as the thin-disk to RIAF transition in black hole accretion regimes.
• Demonstration that LLAGN nuclear emission can be isolated cleanly from host light, enabling robust line ratio diagnostics and accurate measurement of faint coronal lines.
• Evidence that LLAGN in the low-Eddington regime produce hard, yet UV-poor SEDs, lack strong toroidal obscuration, and feature multiphase ISM influenced by mechanical AGN feedback.
• The ReveaLLAGN template set will function as a calibration reference for faint, obscured, or ambiguous AGN detection and SED modeling in both local and high-redshift environments.

As additional data, including NIRSpec/IFU mapping, are incorporated, ReveaLLAGN will further constrain systematic dependencies of coronal-line ratios, molecular gas properties, and outflow energetics on $M_{\rm BH}$ and $L_{\rm bol}/L_{\rm Edd}$, serving as a definitive resource for LLAGN population studies in the JWST era (Goold et al., 2023, Goold et al., 23 Jan 2026).