Can a Satellite Galaxy Merger Explain the Active Past of the Galactic   Center?
  Observations of the Galactic Center (GC) have accumulated a multitude of "forensic" evidence indicating that several million years ago the center of the Milky Way galaxy was teaming with starforming and accretion-powered activity -- this paints a rather different picture from the GC as we understand it today. We examine a possibility that this epoch of activity could have been triggered by the infall of a satellite galaxy into the Milky Way which began at the redshift of 10 and ended few million years ago with a merger of the Galactic supermassive black hole with an intermediate mass black hole brought in by the inspiralling satellite. 
Meagan Lang, Kelly Holley-Bockelmann, Tamara Bogdanovic, Pau   Amaro-Seoane, Alberto Sesana, and Manodeep Sinha
astro-ph.GA astro-ph.CO