VLBI IMAGING OF WATER MASER EMISSION FROM THE NUCLEAR TORUS OF NGC-1068

We have made the first VLBI synthesis images of the H2O maser emission associated with the central engine of the Seyfert galaxy NGC 1068. Em ission extends about +/- 300 km s(-1) from the systemic velocity. Imag es with sub-milliarcsecond angular resolution show that the redshifted emission lies along an are to the northwest of the systemic emission. (The blueshifted emission has not yet been imaged with VLBI.) Based o n the maser velocities and the relative orientation of the known radio jet, we propose that the maser emission arises on the surface of a ne arly edge-on torus, where physical conditions are conducive to maser a ction. The visible part of the torus is axially thick, with comparable height and radius. The velocity field indicates sub-Keplerian differe ntial rotation around a central mass of similar to 1 x 10(7) M. that l ies within a cylindrical radius of about 0.65 pc. The estimated lumino sity of the central engine is about 0.5 of the Eddington limit. There is no detectable compact radio continuum emission near the proposed ce nter of the torus (T-B < 5 x 10(6) K on size scales of similar to 0.1 pc), so that the observed flat-spectrum core cannot be direct self-abs orbed synchrotron radiation.