The IC 133 Water Vapor Maser in the Galaxy M33: A Geometric Distance

We report on the results of a 14 year long VLBI study of proper motions in the IC 133 H2O maser source in the galaxy M33. The method of Ordered Motion Parallax was used to model the 3-dimensional structure and dynamics of IC 133 and obtain a distance estimate, 800 ± 180 kpc. Our technique for determining the distance to M33 is independent of calibrations common to other distance indicators, such as Cepheid Period-Luminosity relations, and therefore provides an important check for previous distance determinations.AnthropologyPhysic