We report the results of a search for 12.2‐GHz methanol maser emission, targeted towards 113 known 6.7‐GHz methanol masers associated with 1.2‐mm dust continuum emission. Observations were carried out with the Australia Telescope National Facility (ATNF) Parkes 64‐m radio telescope in the period 2008 June 20–25. We detect 68 12.2‐GHz methanol masers with flux densities in excess of our 5σ detection limit of 0.55 Jy, 30 of which are new discoveries. This equates to a detection rate of 60 per cent, similar to previous searches of comparable sensitivity. We have made a statistical investigation of the properties of the 1.2‐mm dust clumps with and without associated 6.7‐GHz methanol maser and find that 6.7‐GHz methanol masers are associated with 1.2‐mm dust clumps with high‐flux densities, masses and radii. We additionally find that 6.7‐GHz methanol masers with higher peak luminosities are associated with less dense 1.2‐mm dust clumps than those 6.7‐GHz methanol masers with lower luminosities. We suggest that this indicates that more luminous 6.7‐GHz methanol masers are generally associated with a later evolutionary phase of massive star formation than less luminous 6.7‐GHz methanol maser sources. Analysis of the 6.7‐GHz associated 1.2‐mm dust clumps with and without associated 12.2‐GHz methanol maser emission shows that clumps associated with both class II methanol maser transitions are less dense than those with no associated 12.2‐GHz methanol maser emission. Furthermore, 12.2‐GHz methanol masers are preferentially detected towards 6.7‐GHz methanol masers with associated OH masers, suggesting that 12.2‐GHz methanol masers are associated with a later evolutionary phase of massive star formation. We have compared the colours of the Spitzer Galactic Legacy Infrared Mid‐Plane Survey Extraordinaire (GLIMPSE) point sources associated with the maser sources in the following two subgroups: 6.7‐GHz methanol masers with and without associated 12.2‐GHz methanol masers; and 6.7‐GHz methanol masers with high‐ and those with low‐peak luminosities. There is little difference in the nature of the associated GLIMPSE point sources in any of these subgroups, and we propose that the masers themselves are probably much more sensitive than mid‐infrared data to evolutionary changes in the massive star formation regions that they are associated with. We present an evolutionary sequence for masers in high‐mass star formation regions, placing quantitative estimates on the relative lifetimes for the first time.

The Australia Telescope Compact Array (ATCA) has been used for high angular resolution imaging of 71 southern class I methanol maser sources quasi-simultaneously at 36 and 44 GHz. The data reveal a high level of morphological and kinematical complexity, and allow us to demonstrate associations, at arcsecond precision, of the class I maser emission with outflows, expanding HII regions, dark clouds, shocks traced by the 4.5-µm emission and 8.0-µm filaments. More than 700 maser component features were found at each of the two methanol transitions, but with only 23 per cent recognisable at both transitions; the morphology of class I emission is much better revealed by our survey of both transitions, compared with either one alone. We found that the number of masers falls exponentially with the projected linear distance from the associated class II 6.7-GHz methanol maser. This distribution has a scale of 263±15 mpc, irrespective of the transition. The class I masers associated with OH masers were found to have a tendency to be more spread out, both spatially and in the velocity domain. This is consistent with the expectation that such sources are more evolved. Apart from a small number of high-velocity components (which are largely blue-shifted and predominantly seen at 36 GHz), the velocity distribution was found to be Gaussian, peaking near the systemic velocity of the region, which had been estimated as the middle of the velocity interval of the associated class II methanol maser at 6.7 GHz. The mean indicated a small, but significant blue shift asymmetry of −0.57 km s −1 (uncertainties are 0.06 and 0.07 km s −1 for the 36-and 44-GHz masers, respectively) with respect to the 6.7-GHz masers. The standard deviation of the velocity distribution was found to be 3.65±0.05 and 3.32±0.07 km s −1 for the 36-and 44-GHz masers, respectively. We also suggest a refined rest frequency value of 36169.238±0.011 MHz for the 4 −1 −3 0 E methanol transition.