Infrared and optical emission-line diagnostics

We match the standard NIR classification with four different optical classifications. While there is a broad agreement between the two regimes, there are mismatches and overlaps caused either by aperture effects and/or NIR radiation penetrating obscuring dust and "seeing deeper" into the nuclear region, thus exposing AGN activity.

We examine the relationship between the equivalent widths (EW) of H{alpha} and Pa{beta}, as well as the ratios [NII]/H{alpha} vs. [FeII]/Pa{beta}, and find reasonable correlations. We thus propose a new diagnostic (EW of Pa beta with Fe-WPF) in the NIR (analogous to the WHaN classification), using the [FeII]/Pa{beta} flux ratio and the EW of the Pa{beta} line. We show, within the limitations of the catalogue size, that the regions of the standard NIR diagram can be reasonably replicated in this new scheme.