Abstract
Westerlund 1 (Wd 1) is a highly reddened, massive, compact cluster of post-main sequence stars, including OB supergiants and hypergiants, red and yellow supergiants, and Wolf-Rayet stars. We have examined observations of atomic hydrogen from the Southern Galactic Plane Survey (McClure-Griffiths et al. 2005) to determine the distance to Wd 1 and to investigate its neutral environment. Using the latest Galactic rotation model we derive a distance of 3.9+/-0.7 kpc, which is consistent with a location at the far side of the Scutum-Crux arm. We found a large interstellar bubble of diameter about 50 pc which was created early in the life of the cluster and small expanding bubbles, which we suggest consist of recombined material lost by cluster members through their winds. Additionally we compile a list of kinematic distances to nearby radio bright HII regions and SNRs.
