The Milky Way as a cannibal

Gaia's enormous census of stars in the Milky Way and throughout the Local Group of galaxies will provide a unique set of measurements with which to unravel the early formation and subsequent evolution of the Milky Way.

One application of this data will be to studying the debris of galaxy mergers. Much information about a galaxy can be gleaned from the tidal streams of disrupting dwarf satellites. These streams provide insight into both the progenitor satellite and the dark matter halo of the parent galaxy. Gaia's measurements will provide kinematic data of tidal stream stars which in turn yield the orbit of the stream and the progenitor.

This image is taken from an animation (created by Kathryn V. Johnston) of a simulation of a satellite being torn apart by the Milky Way's tidal field. The simulation followed the satellite's evolution for several billion years. In the image, the Milky Way is represented in blue in the center, with the satellite orbiting around it. In the animation the satellite itself appears much larger than it really is because the images were coloured to emphasize the structure of the debris. This particular image is colour coded to show the density of stars being stripped from the satellite. Further information and the original animations and description are available here.

Image courtesy of Kathyrn V.Johnston.

[Published: 22/09/2003]