Masers identified in March (left), April (centre) and July (right) as listed in Tables 3–5. The bottom panel shows a zoom of the region marked by the dashed grey boxes in the top panels. Each maser is represented by a triangle. The different sizes of the triangles represent the intensity, while the colours indicate the velocity of the maser feature, according to the scale reported in the colour bar. Line segments mark the direction of the polarisation angle for the maser features that show linear polarisation. The average direction of the resulting magnetic field Φ_B obtained for two groups of masers as defined in Sect. 5.2 is indicated in the bottom right corners of each panel. The July observations were in dual circular polarisation only.