galaxy cannibalism

Galaxy cannibalism is the swallowing of a smaller galaxy by a much larger one, in contrast to a galactic merger, which involves two galaxies of similar size. Most examples of cannibalism involve giant or supergiant ellipticals, at the heart of rich clusters of galaxies, drawing in and ingesting other members of their fold. Tell-tale signs of a big elliptical having recently (in cosmic terms) swallowed a disk galaxy, for example, include significant amounts of dust and young stars, loops and shells of luminous matter, and various other phenomena, such as powerful radio emission, that suggests the central supermassive black hole of the swallowing galaxy has just received a fresh consignment of matter. On a less dramatic scale, dwarf galaxies are frequently cannibalized by their larger neighbors. The Sagittarius Dwarf Elliptical Galaxy, for example, is currently being devoured by the Milky Way.