The molecular structure of a starburst - (C-13)O in the nucleus of Maffei 2

We present high-resolution (~6") maps of the ^13^C0 emission in the nucleus of the nearby spiral galaxy Maffei 2 made with the Owens Valley Millimeter Interferometer. The optically thin ^13^CO emission, a tracer of H_2_ gas density, indicates that the molecular cloud distribution in the nucleus of Maffei 2 is remarkably well-correlated with the starburst as traced by radio continuum emission. Evidently the molecular density distribution determines the spatial structure of this starburst. The observed range of ^13^CO emission implies H_2_ column densities of N_H2_ = 0.13-1.3 X 10^32^ cm^-2^, molecular surface densities of σ_H2_ = 200-2000 M_sun_ pc^-2^, and visual extinctions of A_v_ = 14-140 mag on size scales of ~150 pc. The molecular material forms a barlike structure 40" (1 kpc at an assumed distance of 5 Mpc) in extent, with a total H_2_ mass of M_H2_ = 2.3 x 10^8^ M_sun_. Two dynamical components are evident in the ^13^CO maps: a region within ~120 pc of the nucleus that appears to rotate rapidly as a solid body; then nearly Keplerian fall-off to a less-rapidly rotating region extending to a radius of ~500 pc. The most intense star formation activity appears in the inner solid body region of the rotation curve. Within the solid body region, gas accounts for ~40% of the estimated dynamical mass. The centroid of the molecular mass is offset by ~120 pc from the dynamical center of the galaxy. Since the dynamical time scale against winding by differential rotation is ~10^6^ yr, some mechanism must contribute to the longevity of this nuclear bar structure, possibly spiral density waves.