Measuring proper motions of galactic dwarf galaxies with Hubble Space Telescope

摘要

Over the past several years, our research group has been measuring proper motionsfor nearby dwarf satellite galaxies using data taken with the Hubble Space Telescope. In order tomeasure proper motions with an expected size of several tens of milliarcseconds per century usinga time baseline of 2-4 years, our work required that positions of stars and QSOs be measured toan accuracy of '0.25 mas (0.005 pixel). This contribution reviews the scientific justificationof this work and our methodology. It concludes with a few general results and future directions.