Decomposing de mid-infrared emission of AGN to study the disappearance of the torus at the low-luminosity end
Low-luminosity active galactic nuclei (LLAGN) are key to understand the connection (perhaps evolutive) between normal and active galaxies. We have recently found that there are also key to study the connection between the AGN and its host. AGN at mid-infrared are dominated by the clumpy torus emission. However, this torus is expected to disappear below the bolometric luminosity of Lbol=10E+42 erg/s. We have analysed the obscuration of 40 LLAGN (with bolometric luminosities 10E+38 — 10E+43 erg/s) using Spitzer/IRS spectra. We have found for the first time that the torus signatures disappear below the predicted bolometric luminosity (González-Martín et al. 2015). However, this behaviour could also be explained by the preponderance of the host galaxy compared with a weak AGN. We have analysed if the torus has disappeared or diluted by the host emission by the decomposition of the Spitzer/IRS spectra. We have found (1) strong evidence in favor of the smooth vanishment of the torus and (2) an intrinsic difference on the molecular gas content on these objects where the torus is vanishing (Gonzalez-Martin et al. 2016, to be submitted). The implications of these results on the framework of the Unified Model will be discussed.