The radio properties of Seyfert galaxies in the 12 micron and CfA samples

We report the results of 20, 6, and 2 cm VLA and 1.5 cm OVRO observations of two similar radio-quiet active galaxy and quasar (AGN) samples: the optically selected CfA Seyfert galaxies and the bolometric flux-limited 12 mu m active galaxy sample. Every object observed was detected at 6 cm. Only similar to 6%-8% of the 12 mu m sample Seyfert galaxies (three to four objects) are radio-loud (and none of the CfA sample), as compared to 15%-20% for the Bright Quasar Survey quasars. These radio-loud objects are compact and have flat spectra, distinguishing them from the more common radio-quiet objects. The 6-20 cm slopes of the Seyfert 1's and 2's are similar, with average values of [alpha(6 cm)(20)] = -0.66 and -0.71, respectively. Although several Seyfert 1's are significantly flatter than this in their 6-20 and/or 1.5-6 cm slopes, there is no systematic trend for either Seyfert type to display upward or downward spectral curvature. Excluding the radio-loud quasars, the integrated 6 cm radio luminosity is linearly proportional to the 60 mu m luminosity over several orders of magnitude, with on average twice the radio power of normal spirals of the same far-infrared power. About half of the objects show extended 6 cm emission, contributing on average 33% of the total flux. Thus the luminosities of these extended components alone are comparable to normal spirals of similar infrared luminosities. The 12 mu m sample radio luminosity function is slightly higher than that of the CfA sample. The integrated space density of Seyfert 2's is similar to 2 times that of Seyfert 1's over their common range in luminosity. In terms of the standard unified model, this ratio in space density corresponds to a typical half-angle of the torus of theta similar to 48 degrees.