We present the results of a high sensitivity survey for 6.7 GHz methanol masers towards 22 GHz water masers using the 100 m Efflesberg telescope. A total of 89 sources were observed and 10 new methanol masers were detected. The new detections are relatively faint with peak flux densities of between 0.5 and 4.0 Jy. A nil detection rate from low-mass star forming regions enhances the conclusion that the masers are only associated with massive star formation. Even the faintest methanol maser in our survey, with a luminosity of 1.1 × 10 −9 L , is associated with massive stars, as inferred from its infrared luminosity.

The ATCA, MERLIN and VLA interferometers were used to measure the absolute positions of 35 6.7-GHz methanol masers to subarcsecond or higher accuracy. Our measurements represent essential preparatory data for Very Long Baseline Interferometry, which can provide accurate parallax and proper motion determinations of the star-forming regions harboring the masers. Our data also allow associations to be established with infrared sources at different wavelengths. Our findings support the view that the 6.7 GHz masers are associated with the earliest phases of high-mass star formation.

We present a study of molecular outflows using high-resolution mapping of the CO (1-0) line emission toward eight relatively nearby 6.7 GHz methanol masers that are associated with massive star-forming regions. Outflows were detected in seven out of eight sources, and five of them clearly show bipolar or multiple outflow morphologies. These outflows have typical masses of a few solar masses, momenta of tens of M km s À1 , kinetic energies of $10 45 ergs, and mass entrainment rates of a few 10 À5 M yr À1 . They have significantly more mass and kinetic energy than their low-mass counterparts. In some of the sources, the massive outflow is obviously associated with a particular massive star in the cluster, while in others the origin remains uncertain. The high detection rate of outflows toward methanol masers suggests that the outflow phase of massive protostars encompasses the methanol maser phase.