A New Radio Loudness Diagnostic for Active Galaxies: a
  Radio-To-Mid-Infrared Parameter
  We have studied the relationship between the nuclear (high-resolution) radio
emission, at 8.4 GHz (3.6 cm) and 1.4 GHz (20 cm), the [O IV] 25.89um, [Ne III]
15.56um and [Ne II] 12.81um emission lines and the black hole mass accretion
rate for a sample of Seyfert galaxies. In order to characterize the radio
contribution for the Seyfert nuclei we used the 8.4GHz/[O IV] ratio, assuming
that [O IV] scales with the luminosity of the AGN. From this we find that
Seyfert 1's (i.e., Seyfert 1.0's, 1.2's, and 1.5's) and Seyfert 2's (i.e.,
Seyfert 1.8's, 1.9's, and 2.0's) have similar radio contributions, relative to
the AGN. On the other hand, sources in which the [Ne II] emission is dominated
either by the AGN or star formation have statistically different radio
contributions, with star formation dominated sources more "radio loud", by a
factor of ~2.8 on average, than AGN dominated sources. We show that star
formation dominated sources with relatively larger radio contribution have
smaller mass accretion rates. Overall, we suggest that 8.4GHz/[O IV], or
alternatively, 1.4GHz/[O IV] ratios, can be used to characterize the radio
contribution, relative to the AGN, without the limitation of previous methods
that rely on optical observables.
