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Session 36 - Active Galactic Nuclei.
Display session, Tuesday, June 09
Atlas Ballroom,
In the last few years, a number of compact symmetric radio sources have been found to exhibit HI absorption, at or near the systemic velocity, toward the central parsecs. Models proposed to explain this phenomenon involve a circumnuclear torus of gas and dust. The orientation of this structure would determine whether or not the central engine were obscured. Understanding the kinematics of the HI detected toward the central parsecs of these sources will provide an important test of this model and of unified schemes for AGN.
We present results of high resolution VLBA observations at 1.4 GHz toward the active nucleus of NGC 3894, a large elliptical galaxy at z=0.01075. Neutral hydrogen is seen in absorption toward the core, jet, and counterjet of the compact radio source. There are two distinct velocity components in the gas separated by \sim90 km s^-1, both slightly redshifted with respect to the systemic velocity of the galaxy, and there is evidence for additional weaker or unresolved components.
We also present the preliminary results of 1.4 GHz VLBA observations toward 1946+708, a Compact Symmetric Object at z=0.101. These two sources are of particular interest in this project because they both exhibit bi-directional motion measurable on a scale of a few years. This provides unique information about the geometry of these sources, making them ideal targets for studying the distribution of the gas in the central parsecs.
