THE NATURE OF THE DENSE OBSCURING MATERIAL IN THE NUCLEUS OF NGC-1068

We report high spatial and spectral resolution observations of the distribution, physical parameters, and kinematics of the molecular interstellar medium toward the nucleus of the Seyfert 2 galaxy NGC 1068. The data consist of 2.4'' x 3.4'' resolution interferometry of the 88.6 GHz HCN J = 1 --> 0 line at 17 km s-1 spectral resolution, single-dish observations of several millimeter/submillimeter isotopic lines of CO and HCN, and 0.85'' imaging spectroscopy of the 2.12 mum H-2 S(1) line at a velocity resolution of 110 km s-1. The central few hundred parsecs of NGC 1068 contain a system of dense [n(H-2) approximately 10(5) CM-3], warm (T greater-than-or-equal-to 70 K) molecular cloud cores. The low-density molecular envelopes have probably been stripped by the nuclear wind and radiation. The molecular gas layer is located in the plane of NGC 1068's large-scale disk (inclination approximately 35-degrees) and orbits in elliptical streamlines in response to the central stellar bar. The spatial distribution of the 2 mum H-2 emission suggests that gas is shocked at the leading edge of the bar, probably resulting in gas influx into the central 100 pc at a rate of a few M. yr-1. In addition to large-scale streaming (with a solid-body rotation curve), the HCN velocity field requires the presence of random motions of order 100 km s-1. We interpret these large random motions as implying the nuclear gas disk to be very thick (scale height/radius approximately 1), probably as the result of the impact of nuclear radiation and wind on orbiting molecular clouds. The rotation velocities obtained from the HCN map imply that the mass contained within 1 '' of the nucleus is only approximately 1.6 x 10(8) M.. Geometry and column density of the molecular cloud layer between approximately 30 and 300 pc from the nucleus can plausibly account for the nuclear obscuration and anisotropy of the radiation field in the visible and UV.