Rotating toroids in G10.62-0.38, G19.61-0.23, and G29.96-0.02
  Context. In recent years, we have detected clear evidence of rotation in more
than 5 hot molecular cores (HMCs). Their identification is confirmed by the
fact that the rotation axes are parallel to the axes of the associated bipolar
outflows. We have now pursued our investigation by extending the sample to 3
known massive cores, G10.62-0.38, G19.61-0.23, and G29.96-0.02. Aims. We wish
to make a thorough study of the structure and kinematics of HMCs and
corresponding molecular outflows to reveal possible velocity gradients
indicative of rotation of the cores. Methods. We carried out PdBI observations
at 2.7 and 1.4~mm of gas and dust with angular resolutions of 2"-3", and 1"-2",
respectively. To trace both rotation and expansion, we simultaneously observed
CH3CN, a typical HMC tracer, and 13CO, a typical outflow tracer. Results. The
CH3CN(12-11) observations have revealed the existence of clear velocity
gradients in the three HMCs oriented perpendicular to the direction of the
bipolar outflows. For G19 and G29 the molecular outflows have been mapped in
13CO. The gradients have been interpreted as rotating toroids. The rotation
temperatures, used to derive the mass of the cores, have been obtained by means
of the rotational diagram method, and lie in the range of 87-244 K. The
diameters and masses of the toroids lie in the range of 4550-12600 AU, and
28-415 Msun, respectively. Given that the dynamical masses are 2 to 30 times
smaller than the masses of the cores (if the inclination of the toroids with
respect to the plane of the sky is not much smaller than 45 degrees), we
suggest that the toroids could be accreting onto the embedded cluster. For G19
and G29, the collapse is also suggested by the redshifted absorption seen in
the 13CO(2-1) line. We infer that infall onto the embedded (proto)stars must
proceed with rates of 1E-2 Msun/yr, and on timescales of the order of
4E3-1E4yr...
