Low-Luminosity Active Galactic Nuclei (LLAGN) are characterized for low radiative efficiency, much less than one percent of their Eddington limit. Nevertheless, their main energy release may be mechanical, opposite to powerful AGN classes like Seyfert and Quasars. This work reports on the jet-driven mechanical energy and the corresponding mass outflow deposited by the jet in the central 170 parsecs of the nearby LLAGN ESO 428-G14. The jet kinetic output is traced through the coronal line [Si vi] λ19641Å. It is shown that its radial extension, up to hundreds of parsecs, requires a combination of photoionization by the central source and shock excitation as its origin. From the energetics of the ionized gas it is found that the mass outflow rate of the coronal gas is in the range from 3−8 M yr −1 , comparable to those estimated from Hi gas at kiloparsec scales in powerful radio galaxies.

The Event Horizon Telescope (EHT), now with its first ever image of the photon ring around the supermassive blackhole of M87, provides a unique opportunity to probe the physics of supermassive black holes through Very Long Baseline Interferometry (VLBI), such as the existence of the event horizon, the accretion processes as well as jet formation in Low Luminosity AGN (LLAGN). We build a theoretical model which includes an Advection Dominated Accretion Flow (ADAF) with emission from thermal and non-thermal electrons in the flow and a simple radio jet outflow. The predicted spectral energy distribution (SED) of this model is compared to sub-arcsec resolution observations to get the best estimates of the model parameters. The model-predicted radial emission profiles at different frequency bands are used to predict whether the inflow can be resolved by the EHT or with telescopes such as the Global 3-mm VLBI array (GMVA). In this work the model is initially tested with high resolution SED data of M87 and then applied to our sample of 5 galaxies (Cen A, M84, NGC 4594, NGC 3998 and NGC 4278). The model then allows us to predict if one can resolve the inflow for any of these galaxies using the EHT or GMVA.

One distinctive feature of low-luminosity active galactic nuclei (LLAGN) is the relatively weak reflection features they may display in the X-ray spectrum, which can result from the disappearance of the torus with decreasing accretion rates. Some material, however, must surround the active nucleus, i.e., the accretion flow itself and, possibly, a flattened-out or thinned torus. In this work, we study whether reflection is indeed absent or undetectable due to its intrinsically weak features together with the low statistics inherent to LLAGN. Here we focus on NGC 3718 (L/LEdd ∼ 10−5) combining observations from XMM–Newton and the deepest to date NuSTAR (0.5–79 keV) spectrum of a LLAGN, to constrain potential reflectors, and analyze how the fitted coronal parameters depend on the reflection model. We test models representing both an accretion disc (Relxill) and a torus-like (MYTorus and Borus) neutral reflector. From a statistical point of view, reflection is not required, but its inclusion allows to place strong constraints on the geometry and physical features of the surroundings: both neutral reflectors (torus) tested should be Compton thin (NH < 1023.2cm−2) and preferentially cover a large fraction of the sky. If the reflected light instead arises from an ionized reflector, a highly ionized case is preferred. These models produce an intrinsic power-law spectral index in the range [1.81–1.87], where the torus models result in steeper slopes. The cut-off energy of the power-law emission also changes with the inclusion of reflection models, resulting in constrained values for the disc reflectors and unconstrained values for torus reflectors.

According to theory, the torus of active galactic nuclei (AGN) is sustained from a wind coming off the accretion disk, and for low efficient AGN, it has been proposed that such structure disappears. However, the exact conditions for its disappearance remain unclear. This can be studied throughout the reflection component at X-rays, which is associated with distant and neutral material at the inner walls of the torus in obscured AGN. We select a sample of 81 AGNs observed with NuSTAR with a distance limit of D< 200 Mpc and Eddington rate $\rm {\lambda _{Edd} \equiv L_{bol}/L_{Edd}<10^{-3}}$. We fit the 3-70 keV spectra using a model accounting for a partial-covering absorber plus a reflection component from neutral material. We find that the existence of the reflection component spans in a wide range of black hole mass and bolometric luminosities, with only ∼13 per cent of our sample (11 sources) lacking of any reflection signatures. These sources fall in the region in which the torus may be lacking in the L-MBH diagram. For the sources with a detected reflection component, we find that the vast majority of them are highly obscured ($\rm {\log \ N_H > 23}$), with $\rm {\sim 20{{\ \rm per\ cent}}}$ being Compton-thick. We also find an increase on the number of unobscured sources and a tentative increase on the ratio between $\rm {FeK\alpha }$ emission line and Compton-hump luminosities toward $\rm {\lambda _{Edd}=10^{-5}}$, suggesting that the contribution of the $\rm {FeK\alpha }$ line changes with Eddington ratio.