The structure of the molecular gas in the young planetary nebula NGC 2346.

The CO J = 2-1 and J = 1-0 emission in the bipolar planetary nebular NGC 2346 has been mapped with a 12 arcmin resolution. The CO emission contours are shown to follow the main distribution of the ionized gas. It is found that the dense gas constitutes the walls of a cavity with a clumped structure, with prominent clumps concentrated on an expanding ring which surrounds the central star. The ring is tilted about 56 deg with respect to the line of sight and has an expansion velocity of 18 km/s and a kinematic age of about 1600 yr. The total mass of the molecular gas in the nebula is about 0.1 solar masses. The possible origin of the nebula morphology is examined. It is suggested that an interacting wind model may explain the observations.