A New Photoionization Model of the Narrow Line Region in Active Galactic Nuclei

Abstract: The photoionization model of narrow-line regions (NLRs) in active galactic nuclei (AGNs) has been investigated for decades. Many published models are restricted to simple linear scaling abundance relations, dust-free assumption, uniform AGN radiation field, and using one specific photoionization code, which restricts them from providing a satisfactory prediction on a broad range of AGN observations. Through a comprehensive investigation, here we present how the choice of abundance scaling relations, dust inclusion, AGN radiation fields, and different photoionization codes CLOUDY and MAPPINGS affect the predictions on the strength of strong UV, optical, and infrared emission lines. We find the dust-depleted radiation pressure-dominated AGN model built with the latest non-linear abundance sets and photoionization code MAPPINGS V are consistent with AGN observations across a broad range of wavelengths. We also assess new potential HII-AGN separation diagrams in the optical and UV wavelengths.