The torus, which surrounds the nucleus of M 2-9, has a mean diameter of about 6''. Its symmetry axis is tilted by with respect to the plane of the sky. The de-projected expansion velocity is , and its kinematical age is about 2100 years assuming a distance of 1 kpc. The lower limit for the total mass of the molecular gas is estimated to be , i.e. at least comparable to the ionized mass in the nebula (Figure 1).
Figure: Maps of the intensity for the LSR velocities indicated in the upper left corner of each box (contours: 72 ( ), 144, 216, 288, and ). The spatial units are offsets in arcseconds with respect to the assumed position for the central star. Up is north and left is east. The Gaussian clean beam ( at a position angle of ) is inserted in the lower left map. In order to increase the signal to noise ratio in the maps we smoothed the channels to a velocity resolution of . The r.m.s. noise in the maps is about .