Seyfert galaxies: Nuclear radio structure and unification

Abstract

We have observed a sample of Seyfert (Sy) galaxies with global Very Long Baseline Interferometry (VLBI) to test predictions of the unification scheme which hypothesizes 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 axisymmetric active nucleus with respect to the observer, then, the parsec-scale radio structures of the two types should be similar. We chose a sample of 10 Sy Is 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 orientationindependent parameters viz., host galaxy properties and measures of intrinsic power of the active nucleus. We present the results obtained from these observations and their implications for the unification scheme. We also discuss the results obtained from the measurements at all IRAS and 2-10 keY X-ray wavebands for our Sy galaxy sample using data from the literature.