Kathryn Johnston, Columbia University
The existence of spectacular low-surface-brightness features – remnants of past mergers – surrounding many galaxies has been known about for many decades. A major accomplishment for more recent, large scale stellar surveys of the Milky Way has been the discovery of a multitude of debris from dead and dying small satellites encircling our own Galaxy. While these structures contain less than 1% of the light in the Universe and an even smaller fraction of the total mass their properties can be used to address fundamental topics, such as the shape, mass and extent of dark matter halos and the process of hierarchical structure formation. This talk will look at just a few examples of such applications.