The Influence of Black Hole Mass and Accretion Rate on the FRI/FRII Radio Galaxy Dichotomy

We use medium resolution optical spectra of 3CR radio galaxies to estimate their black hole masses and accretion rates. Black hole masses are found from central stellar velocity dispersions, and accretion rates are derived from narrow emission-line luminosities. The sample covers both Fanaroff-Riley (FR) classes; the more powerful FRIIs and the less powerful FRIs. We find that FRIs and FRIIs separate in diagrams of radio luminosity and narrow-line luminosity versus black hole mass. This suggests that, at a given black hole mass, the FRIIs accrete more efficiently, or accrete more matter, than FRIs.