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.

We present the second portion of an unbiased survey of the Galactic plane for 6668‐MHz methanol masers. This section of the survey spans the longitude range 6° to 20°. We report the detection of 119 maser sources, of which 42 are new discoveries. The masers are tightly constrained to the Galactic plane, with only four outside a latitude range of ±1°. This longitude region includes the brightest known 6668‐MHz methanol maser, 9.621+0.196, as well as the two brightest newly discovered sources in the southern survey as a whole. We list all the sources associated with the 3‐kpc arms within ±15° longitude and consider further candidates beyond 15° longitude. We identify three new sources associated with the Galactic bar and comment on the density of masers in relation to the bar orientation.

We present first results of the H2O Southern Galactic Plane Survey (HOPS), using the Mopra Radio Telescope with a broad‐band backend and a beam size of about 2 arcmin. We have observed 100 deg2 of the southern Galactic plane at 12 mm (19.5–27.5 GHz), including spectral line emission from H2O masers, multiple metastable transitions of ammonia, cyanoacetylene, methanol and radio recombination lines. In this paper, we report on the characteristics of the survey and H2O maser emission. We find 540 H2O masers, of which 334 are new detections. The strongest maser is 3933 Jy and the weakest is 0.7 Jy, with 62 masers over 100 Jy. In 14 maser sites, the spread in the velocity of the H2O maser emission exceeds 100 km s−1. In one region, the H2O maser velocities are separated by 351.3 km s−1. The rms noise levels are typically between 1 and 2 Jy, with 95 per cent of the survey under 2 Jy. We estimate completeness limits of 98 per cent at around 8.4 Jy and 50 per cent at around 5.5 Jy. We estimate that there are between 800 and 1500 H2O masers in the Galaxy that are detectable in a survey with similar completeness limits to HOPS. We report possible masers in NH3 (11,9) and (8,6) emission towards G19.61−0.23 and in the NH3 (3,3) line towards G23.33−0.30.

We present the fifth portion of an unbiased survey of the Galactic plane, |b| ≤ 2• , for 6668-MHz methanol masers. This section of the survey completes the Galactic longitude range visible to the Parkes radio telescope, incorporating the longitude range 20• -60• . Within this section of the survey we find 265 methanol masers, 64 new to the survey, bringing the total number of methanol masers detected across the full longitude coverage (186• , through 0 • , to 60 • ) to 972 sources.

We have conducted a Galactic plane survey of methanol masers at 6668 MHz using a seven‐beam receiver on the Parkes telescope. Here we present results from the first part, which provides sensitive unbiased coverage of a large region around the Galactic Centre. Details are given for 183 methanol maser sites in the longitude range 345° through the Galactic Centre to 6°. Within 6° of the Galactic Centre, we found 88 maser sites, of which more than half (48) are new discoveries. The masers are confined to a narrow Galactic latitude range, indicative of many sources at the Galactic Centre distance and beyond, and confined to a thin disc population; there is no high‐latitude population that might be ascribed to the Galactic bulge. Within 2° of the Galactic Centre the maser velocities all lie between −60 and +77 km s−1, a range much smaller than the 540 km s−1 range observed in CO. Elsewhere, the maser with highest positive velocity (+107 km s−1) occurs, surprisingly, near longitude 355° and is probably attributable to the Galactic bar. The maser with the most negative velocity (−127 km s−1) is near longitude 346°, within the longitude–velocity locus of the near side of the ‘3‐kpc arm’. It has the most extreme velocity of a clear population of masers associated with the near and far sides of the 3‐kpc arm. Closer to the Galactic Centre the maser space density is generally low, except within 0.25 kpc of the Galactic Centre itself, the ‘Galactic Centre zone’, where it is 50 times higher, which is hinted at by the longitude distribution, and confirmed by the unusual velocities.

We present the fourth portion of a Galactic plane survey of methanol masers at 6668 MHz, spanning the longitude range 186 • -330 • . We report 207 maser detections, 89 new to the survey. This completes the southern sky part of the methanol multibeam survey and includes a large proportion of new sources, 43 per cent. We also include results from blind observations of the Orion-Monoceros star-forming region, formally outside the latitude range of the methanol multibeam survey; only the four previously known methanol emitting sites were detected, of which we present new positions and spectra for masers at Orion A (south) and Orion B, obtained with the Multi-Element Radio Linked Interferometer Network (MERLIN) array.

We present results from the third portion of the Methanol Multibeam Galactic plane survey of masers at 6668 MHz. It covers the longitude range 330°–345°, yielding 198 masers, of which more than 40 per cent are new discoveries. The maser population in this longitude range is the densest anywhere in the Galaxy, with many sources delineating a large portion of the Norma spiral arm close to its tangent point, and a cluster defining the southern tangent point of the 3‐kpc ring. Two sources lie outside the solar circle, on the far side of the Galaxy, more than 15 kpc away.