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 a method to derive positions of molecular clouds along the lines of sight from a quantitative comparison between 2.6‐mm CO emission lines and 18‐cm OH absorption lines, and apply it to the central kiloparsecs of the Milky Way. With some simple but justifiable assumptions, we derive a face‐on distribution of the CO brightness and corresponding radial velocity in the Galactic Centre without any help of kinematical models. The derived face‐on distribution of the gas is elongated and inclined so that the Galactic‐eastern (positive longitude) side is closer to us. The gas distribution is dominated by a bar‐like central condensation, whose apparent size is 500 × 200 pc. A ridge feature is seen to stretch from one end of the central condensation, though its elongated morphology might be artificial. The velocity field shows clear signs of non‐circular motion in the central condensation. The ‘expanding molecular ring’ feature corresponds to the peripheral region surrounding the central condensation, with the Galactic‐eastern end being closer to us. These characteristics agree with a picture in which the kinematics of the gas in the central kiloparsec of the Galaxy is under the strong influence of a barred potential. The face‐on distribution of the in situ pressure of the molecular gas is derived from the CO multiline analysis. The derived pressure is found to be highest in the central 100 pc. In this region, the gas is accumulating and is forming stars.

A new seven‐beam 6–7 GHz receiver has been built to survey the Galaxy and the Magellanic Clouds for newly forming high‐mass stars that are pinpointed by strong methanol maser emission at 6668 MHz. The receiver was jointly constructed by Jodrell Bank Observatory (JBO) and the Australia Telescope National Facility (ATNF) and allows simultaneous coverage at 6668 and 6035 MHz. It was successfully commissioned at Parkes in 2006 January and is now being used to conduct the Parkes–Jodrell multibeam maser survey of the Milky Way. This will be the first systematic survey of the entire Galactic plane for masers of not only 6668‐MHz methanol, but also 6035‐MHz excited‐state hydroxyl. The survey is two orders of magnitude faster than most previous systematic surveys and has an rms noise level of ∼0.17 Jy. This paper describes the observational strategy, techniques and reduction procedures of the Galactic and Magellanic Cloud surveys, together with deeper, pointed, follow‐up observations and complementary observations with other instruments. It also includes an estimate of the survey detection efficiency. The 111 d of observations with the Parkes telescope have so far yielded >800 methanol sources, of which ∼350 are new discoveries. The whole project will provide the first comprehensive Galaxy‐wide catalogue of 6668‐MHz and 6035‐MHz masers.

We present MERLIN maps of the 22-GHz H 2 O masers around four low-mass late-type stars (IK Tau, U Ori, RT Vir and U Her), made with an angular resolution of ∼15 milliarcsec and a velocity resolution of 0.1 km s −1 . The H 2 O masers are found in thick expanding shells with inner radii ∼6 to 16 au and outer radii four times larger. The expansion velocity increases radially through the H 2 O maser regions, with logarithmic velocity gradients of 0.5-0.9. IK Tau and RT Vir have well-filled H 2 O maser shells with a spatial offset between the near and far sides of the shell, which suggests that the masers are distributed in oblate spheroids inclined to the line of sight. U Ori and U Her have elongated poorly filled shells with indications that the masers at the inner edge have been compressed by shocks; these stars also show OH maser flares. MERLIN resolves individual maser clouds, which have diameters of 2-4 au and filling factors of only ∼0.01 with respect to the whole H 2 O maser shells. The circumstellar envelope velocity structure gives additional evidence the maser clouds are densitybounded. Masing clouds can be identified over a similar time-scale to their sound crossing time (∼2 yr) but not longer. The sizes and observed lifetimes of these clouds are an order of magnitude smaller than for those around red supergiants, similar to the ratio of low-mass:high-mass stellar masses and sizes. This suggests that cloud size is determined by stellar properties, not local physical phenomena in the wind.