Pair-matching of radio-loud and radio-quiet AGNs
  Active galactic nuclei (AGNs) are known to cover an extremely broad range of
radio luminosities and the spread of their radio-loudness is very large at any
value of the Eddington ratio. This implies very diverse jet production
efficiencies which can result from the spread of the black hole spins and
magnetic fluxes. Magnetic fluxes can be developed stochastically in the
innermost zones of accretion discs, or can be advected to the central regions
prior to the AGN phase. In the latter case there could be systematic
differences between the properties of galaxies hosting radio-loud (RL) and
radio-quiet (RQ) AGNs. In the former case the differences should be negligible
for objects having the same Eddington ratio. To study the problem we decided to
conduct a comparison study of host galaxy properties of RL and RQ AGNs. In this
study we selected type II AGNs from SDSS spectroscopic catalogues. Our RL AGN
sample consists of the AGNs appearing in the Best & Heckman (2012) catalogue of
radio galaxies. To compare RL and RQ galaxies that have the same AGN parameters
we matched the galaxies in black hole mass, Eddington ratio and redshift. We
compared several properties of the host galaxies in these two groups of objects
like galaxy mass, colour, concentration index, line widths, morphological type
and interaction signatures. We found that in the studied group RL AGNs are
preferentially hosted by elliptical galaxies while RQ ones are hosted by
galaxies of later type. We also found that the fraction of interacting galaxies
is the same in both groups of AGNs. These results suggest that the magnetic
flux in RL AGNs is advected to the nucleus prior to the AGN phase.
