Testing the Unified Model with an Infrared Selected Sample of Seyfert Galaxies

Abstract

We present a series of statistical tests done to a sample of 29 Seyfert 1 and 59 Seyfert 2 galaxies selected from mostly isotropic properties, their far infrared fluxes and warm infrared colors. Such selection criteria provide a profound advantage over the criteria used by most investigators in the past, such as ultraviolet excess. These tests were done using ground based high resolution VLA A-configuration 3.6 cm radio and optical B and I imaging data. From the relative number of Seyfert 1's and Seyfert 2's we calculate that the torus half opening angle is 48deg. We show that, as seen in previous papers, there is a lack of edge-on Seyfert 1 galaxies, suggesting dust and gas along the host galaxy disk probably play an important role in hiding some nuclei from direct view. We find that there is no statistically significant difference in the distribution of host galaxy morphological types and radio luminosities of Seyfert 1's and Seyfert 2's, suggesting that previous results showing the opposite may have been due to selection effects. The average extension of the radio emission of Seyfert 1's is smaller than that of Seyfert 2's by a factor of ~2-3, as predicted by the Unified Model. A search for galaxies around our Seyferts allows us to put a lower and an upper limit on the possible number of companions around these galaxies of 19% and 28%, respectively, with no significant difference in the number of companion galaxies between Seyfert 1's and Seyfert 2's. We also show that there is no preference for the radio jets to be aligned closer to the host galaxy disk axis in late type Seyferts, unlike results claimed by previous papers. These results, taken together, provide strong support for a Unified Model in which type 2 Seyferts contain a torus seen more edge-on than the torus in type 1 Seyferts.