The Merging History of the Milky Way Disk
  The stellar populations of the stellar halo and of the thick disk of the Milky Way reveal much about the merging history that our Galaxy, a typical large disk galaxy, has experienced. Our current understanding, described here, implies a rather quiet evolution for the disk, back to redshifts of order 2. 
Rosemary F.G. Wyse (Johns Hopkins Univ)