Insight Into the Formation of the Milky Way Through Cold Halo Substructure. I. The ECHOS of Milky Way Formation

Understand

We identify ten -- seven for the first time -- elements of cold halo substructure (ECHOS) in the volume within 17.5 kpc of the Sun in the inner halo of the Milky Way.

• Our result is based on the observed spatial and radial velocity distribution of metal-poor main sequence turnoff (MPMSTO) stars in 137 Sloan Extension for Galactic Understanding and Exploration (SEGUE) lines of sight.
• We point out that the observed radial velocity distribution is consistent with a smooth stellar component of the Milky Way's inner halo overall, but disagrees significantly at the radial velocities that correspond to our detections.
• We show that all of our detections are statistically significant and that we expect no false positives.