All the big galaxies in the universe sooner or later end up cannibalizing one of their smaller companions, stealing gas and stars over millions of years. A new study, published in the Astrophysical Journal Letters, shows that size doesn’t matter to become a galactic cannibal. Even smaller galaxies can do that.
Francesca Annibali of INAF, the Italian National Institute for Astrophysics, and her colleagues used the Large Binocular Telescope (LBT)to observe a curious dwarf galaxy called DDO 68.
"When we analyzed our Hubble Space Telescope images, we detected an anomalous protuberance off DDO 68's main body," said Annibali in a statement
“We thought that only LBT with its two 8.4 meter primary mirrors could have the power and the field of view necessary to prove, or disprove, the presence of a stream and other accreting satellites."
DDO 68 is a special object. It is located in a cosmic “void” away from other galaxies and its chemical composition has not changed much since the Big Bang. The galaxy has a mass of 100 million solar masses, about 10,000 times less than the Milky Way.
Apart from the stream of stars, dust and gas coming out of DDO 68, the galaxy is also surrounded by several smaller companions, with a likely mass of 100,000 suns. Without any bigger galaxies around, it’s up to DDO 68 to eat the smaller objects.
"This is the first evidence of a stellar stream around an isolated dwarf galaxy of only a hundred million solar masses, and the observational proof that hierarchical galaxy formation processes work also at the smallest scales," said Annibali.
"In other words, not only massive bodies are able to cannibalize the smaller ones that happen to lie in their surroundings, but the same appetite and digestion capabilities can be found in the smaller ones," added Monica Tosi, INAF astronomer and member of Annibali’s team.
It is now evident that, when it comes to galaxy evolution, there’s plenty of room at the bottom.