Distances to southern 6.7-GHz methanol masers through H i self-absorption

We present the kinematic distance ambiguity resolutions of over 400 6.7-GHz methanol masers. Using the data sets of the International Galactic Plane Survey we have extracted H I spectra towards the sites of methanol maser emission between longitudes 270 and 67 and examined them for evidence of H I self-absorption. Using well-established criteria we identify 442 resolutions (classified by reliability) with a 1.07:1.11 ratio between near and far kinematic distance assignments. For a sub-sample of 118, we compare our resolutions with those of the literature and find 85 10 per cent agreement. Using the distances we examine the Galactocentric distribution and properties of the masers. We also compare 6.7-GHz maser velocities with those of CS, finding the maser mid-velocity is closely correlated with the CS velocity, typically to within 2.8 km s -1 .