On the age of field halo stars (Jofre & Weiss, 2011)
  A study of stellar ages of a sample from the Sloan Digital Sky Survey (SDSS) is presented. The results are consolidated with a set of globular clusters (GCs) and show that this stellar sample is composed by one dominant population of 10-12 Gyr old. This supports the Eggen's scenario claiming that the inner halo of the Milky Way formed rapidly, probably during the collapse of the proto-Galactic cloud. 
Paula Jofre
astro-ph.GA