Is there really a dichotomy in AGN jet power?
  To gain new insights into the radio-loud/radio-quiet dichotomy reported for
active galactic nuclei, we examine radio loudness as a function of Eddington
ratio for a previously published sample of 199 AGN from five different
populations. After initially considering radio loudnesses derived using total
radio luminosities, we repeat the investigation using core radio luminosities
only, applying a previously established mass correction for these core
luminosities. In both cases, for Eddington ratios < 1 per cent, Fanaroff-Riley
type I and broad-line radio galaxies are on average more radio-loud than
Seyfert and low-ionization nuclear emission-line region galaxies. However, the
distribution of radio loudnesses for the mass-corrected, core-only sample is
much narrower than that of the clearly bimodal total radio loudness
distribution. The advantages and disadvantages of using core- or lobe-dominated
radio luminosity as a measure of instantaneous jet power are discussed. We
furthermore compare the core and total radio luminosities for the entire
sample, as well as illustrating the importance of the mass term by comparing
the AGN with a sample of black hole X-ray binaries. We conclude that if the
mass-corrected core radio luminosity is a good measure of jet power, then black
hole spin may have considerably less impact on jet power than previously
reported, or that our sample does not include the extremes of spin. If the
spread in jet power is small then we suggest that characteristics of the
ambient environment and/or the radio source age could be equally as important
in producing a radio-loud/radio-quiet dichotomy seen in total radio luminosity.
