Seyfert galaxies: Nuclear Radio Structure and Unification

Abstract

We have observed a sample of Seyfert (Sy) galaxies with the global Very Long Baseline Interferometry (VLBI) to test the predictions of the unification scheme for the Sy galaxies which hypothesises that Sys of Type 1 and of Type 2 constitute a single population of objects. If Sy 1 and Sy 2 galaxies differ only in the orientation of the axisymmmetric active nucleus with respect to the observer, then, the parsec scale radio structures of the two types should be similar. The overall goal of the thesis is to rigorously test the predictions of the unified scheme hypothesis for the Sy galaxies. We chose a sample of 10 Sy 1s and 10 Sy 2s such that the two subsamples were intrinsically similar within the framework of the unified scheme. This was done by matching them as far as possible in the orientation-independent parameters {\it viz.}, host galaxy properties and measures of intrinsic Active Galactic Nuclei (AGN) power. We here present the results obtained from these observations and their implications on the unification scheme. We also discuss the results obtained from the measurements at all IRAS and 2-10 keV X-ray wavebands for our Sy galaxy sample using data from the literature.