Galactic Cannibalism

The life and death of satellite galaxies


What happens when a single satellite galaxy is torn apart by tidal forces from the parent galaxy it is orbiting? Numerical modeling (e.g. as shown in the image to the right) reveals that debris torn from the smaller galaxy forms streams of stars both leading and trailing the satellite along its orbit. Coincident to this early theoretical work, a satellite in the middle of being cannibalized by the Milky Way was discovered (the Sagittarius dwarf galaxy) with structure curiously reminiscent of the simulations.

Because of the simple dynamics of tidal debris it is easy to model, and, as a consequence, it can be used as a powerful probe not only of the destroyed satellite's history (mass, mass-loss rate and orbit), but also of size, shape and lumpiness of the parent galaxy it is orbiting.