Imaging HI Absorption toward Symmetric Radio Galaxies - Evidence for a Circumnuclear Torus

Abstract

Recent VLBI observations have identified several compact radio sources which have symmetric structures on parsec scales, and exhibit HI absorption which appears to be associated with the active nucleus. These sources are uniquely well suited to investigations into the physics of the central engines, in particular to studies of the kinematics of the gas within 100 pc of the core. In these compact sources, it is reasonable to assume that this circumnuclear material is accreting onto, and ``feeding'', the central engine. We present results of HI imaging studies of 3 symmetric radio galaxies which show evidence of a circumnuclear torus.