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Context. In recent years, we have detected clear evidence of rotation in morethan 5 hot molecular cores (HMCs). Their identification is confirmed by thefact that the rotation axes are parallel to the axes of the associated bipolaroutflows. We have now pursued our investigation by extending the sample to 3known massive cores, G10.62-0.38, G19.61-0.23, and G29.96-0.02. Aims. We wishto make a thorough study of the structure and kinematics of HMCs andcorresponding molecular outflows to reveal possible velocity gradientsindicative of rotation of the cores. Methods. We carried out PdBI observationsat 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 observedCH3CN, a typical HMC tracer, and 13CO, a typical outflow tracer. Results. TheCH3CN(12-11) observations have revealed the existence of clear velocitygradients in the three HMCs oriented perpendicular to the direction of thebipolar outflows. For G19 and G29 the molecular outflows have been mapped in13CO. The gradients have been interpreted as rotating toroids. The rotationtemperatures, used to derive the mass of the cores, have been obtained by meansof the rotational diagram method, and lie in the range of 87-244 K. Thediameters and masses of the toroids lie in the range of 4550-12600 AU, and28-415 Msun, respectively. Given that the dynamical masses are 2 to 30 timessmaller than the masses of the cores (if the inclination of the toroids withrespect to the plane of the sky is not much smaller than 45 degrees), wesuggest that the toroids could be accreting onto the embedded cluster. For G19and G29, the collapse is also suggested by the redshifted absorption seen inthe 13CO(2-1) line. We infer that infall onto the embedded (proto)stars mustproceed with rates of 1E-2 Msun/yr, and on timescales of the order of4E3-1E4yr...

Rotating toroids in G10.62-0.38, G19.61-0.23, and G29.96-0.02