A Cigale module tailored (not only) for Low-Luminosity AGN

Abstract: The spectral energy distribution (SED) of low-luminosity active galactic nuclei (LLAGN) presents challenges due to their faint emissions and the complexity of their accretion processes. This study introduces a new CIGALE module tailored for LLAGN, combining the empirical $L_X$-$L_{12\mu m}$ relationship with physical models like advection-dominated accretion flows (ADAFs) and truncated accretion disks. This module yields a refined depiction of LLAGN emissions, and a mock analysis shows reliable parameter recovery, with only minor biases. We tested the module on a sample of 50 X-ray-detected local galaxies, including LINERs and Seyferts, where it demonstrated good estimation of bolometric luminosities, even in the presence of significant galaxy contamination. Notably, the previous X-ray module failed to provide AGN solutions for this sample, stressing the need for a novel approach. Comparisons with mid-luminosity AGN confirm the module's robustness and applicability to AGN up to $L_X$ < $10^{45}$ erg/s. We also expanded the X-ray to bolometric correction formula, making it applicable to AGN spanning ten orders of magnitude in luminosity, and revealing lower $k_X$ values than typically assumed. Additionally, our analysis of the $\alpha_{ox}$ index, representing the slope between UV and X-ray emissions, uncovered trends that differ from those observed in high-luminosity AGN, suggesting a shift in accretion physics and photon production mechanisms in low-luminosity regimes. These results underscore the importance of a multiwavelength approach in AGN studies and reveal distinct behaviors in LLAGN compared to quasars. Our findings significantly advance the understanding of LLAGN and offer a comprehensive framework for future research aimed at completing the census of the AGN population.