Figure 1 (adapted from Stern & Laor 2013):
The optical narrow line ratios of type 1 AGN. The contours show the distribution of 3,200 low-redshift type 1 AGN, selected from the SDSS quasar and galaxy samples based on the detection of broad Hα emission. The background greyscale shows the distribution of type 2 AGN from Kewley et al. (2006). The lines mark the standard divisions of the galaxies into sub-groups (sub-groups names noted in panels). Notice the group of type 1 AGN with high [OIII]/Hβ, low [NII]/Hα, and low [SII]/Hα, which have no corresponding match in the type 2 AGN sample.
Covering Factor vs. AGN Luminosity
Figure 2 (adapted from Stern & Laor 2012):
The average Hα spectra of type 1 AGN, as a function of broad line luminosity (different rows) and broad line width (different columns). The background grey dots denote the distribution of the objects used to create the mean spectra, in the plane of line luminosity versus line width. Notice how the narrow emission lines become relatively stronger with decreasing luminosity. This result suggests that the typical low-luminosity is AGN is an ‘intermediate type’ AGN.