Black Hole Mass and Eddington Ratio as Drivers for the Observable Properties of Radio‐loud and Radio‐quiet QSOs

Recent studies of black holes in the nuclei of both active and normal galaxies have yielded relationships that permit a physical interpretation of the principal components of the spectra of QSOs. It is shown that principal component (or eigenvector) 1 (PC1) is driven predominantly by L/LEdd, and principal component 2 (PC2) is driven by accretion rate. This results in a PC2 vs. PC1 diagram in which lines of constant black hole mass are diagonal. Using a sample consisting of the low-redshift PG objects supplemented by 75 radio-loud QSOs, it is shown that such a diagram effectively distinguishes radio-loud from radio-quiet objects as well as demonstrating that both narrow-line Seyfert 1s and broad absorptionline QSOs lie at the high L/LEdd extreme, though these two types of objects are well separated in the PC2 direction. A simple picture that ties together physical parameters (black hole mass and Eddington ratio) and classification of AGN is presented. Based on the location of core-dominated and lobe-dominated radioloud QSOs, orientation can be modeled as a third parameter in this scheme, implying an enhancement in the radio flux of core-dominated objects. Subject headings: galaxies: Seyfert—galaxies: nuclei—quasars: general