A new dual-component photoionization model for the narrow emission line regions in active galactic nuclei

Having found that type 1 Seyfert nuclei have excess [Fe VII] lambda 6087 em ission with respect to type 2 nuclei, Murayama & Taniguchi have proposed th at the high-ionization nuclear emission line region (HINER) traced by the [ Fe VII] lambda 6087 emission resides in the inner wall of dusty tori. The c overing factor of the torus is usually large (e.g., similar to 0.9). Furthe r, electron density in the tori (e.g., similar to 10(7)-10(8) cm(-3)) is co nsidered to be significantly higher than that (e.g., similar to 10(3)-10(4) cm(-3)) in the narrow-line region(NLR). Therefore, it is expected that the torus emission contributes to the majority of the higher ionization emissi on lines. Taking this MINER component into account, we have constructed new dual-component (i.e., a typical NLR with a MINER torus) photoionization mo dels. Comparison of our model with the observations shows that if the torus emission contributes similar to 10% of the NLR emission, our dual-componen t model can explain the observed high [Fe VII] lambda 6087/[O III] lambda 5 007 intensity ratios of the Seyfert 1 nuclei without invoking any unusual a ssumptions (e.g., the overabundance of iron).