A massive mess: When a large dwarf and a Milky Way-like galaxy merge

Understand

Circa 10 billion years ago the Milky Way merged with a massive satellite, Gaia-Enceladus.

• To gain insight into the properties of its debris we analyse in detail the suite of simulations from Villalobos & Helmi (2008), which includes an experiment that produces a good match to the kinematics of nearby halo stars inferred from Gaia data.
• We compare the kinematic distributions of stellar particles in the simulations and study the distribution of debris in orbital angular momentum, eccentricity and energy, and its relation to the mass-loss history of the simulated satellite.
• We confirm that Gaia-Enceladus probably fell in on a retrograde, 30$^\circ$ inclination orbit.