J=1-0 synthesis images of a dense torus in M 2-9
, R. Neri , R. Bachiller 
,
V. Bujarrabal , M. Grewing Institut de Radio Astronomie Millimétrique (IRAM), 300 Rue
de la Piscine, F-38406 Saint Martin d'Hères, France Observatorio Astronómico Nacional (I.G.N), Apartado 1143, E-28800 Alcalá de Henares,
Madrid, Spain 
emission in the bipolar
planetary nebula M 2-9 using the IRAM interferometer. From the maps
we were able to investigate in detail the morphology and the
kinematics of the molecular gas. The data are best explained by
assuming that the molecular gas is concentrated in an expanding,
clumpy torus.
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 
.