2015MNRAS.448.2900R

We introduce Coronal-Line Forest active galactic nuclei (CLiF AGN), AGN which have a rich spectrum of forbidden high-ionization lines (FHILs, e.g. [Fevii], [Fex] and [Nev]), as well as relatively strong narrow ( ∼ 300 km/s) Hα emission when compared to the other Balmer transition lines. We find that the kinematics of the CLiF emitting region are similar to those of the forbidden low-ionization emission-line (FLIL) region. We compare emission line strengths of both FHILs and FLILs to cloudy photoionization results and find that the CLiF emitting region has higher densities (104.5 < nH < 10^7.5/ cm3) when compared to the FLIL emitting region (103.0 < nH < 10^4.5/ cm3). We use the photoionization results to calculate the CLiF regions radial distances (0.04 < RCLiF < 32.5 pc) and find that they are comparable to the dust grain sublimation distances (0.10 < RSUB < 4.3 pc). As a result, we suggest that the inner torus wall is the most likely location of the CLiF region, and the unusual strength of the FHILs is due to a specific viewing angle giving a maximal view of the far wall of the torus without the continuum being revealed.