Title: The LAMOST view of Galactic halo substructure

Abstract:
The LAMOST survey will obtain spectra of more than 5 million Milky Way stars over its five-year 
duration. This massive survey will provide statistically complete samples of most Galactic 
stellar populations over much of the northern hemisphere accessible from its location in 
northeastern China. The spectra from LAMOST have resolution R~1800 over a wavelength range 
of 3700-9000 Angstroms, similar to those of SDSS/SEGUE. We present early results based on 
the first year (plus pilot survey) data, which include stellar parameters from ~2.2 million stellar 
spectra, mostly of stars brighter than r~17. Despite the relatively bright limiting magnitude, the 
sheer number of spectra being obtained inevitably includes large samples of Galactic halo 
giants, including many in known tidal substructures such as the Sagittarius tidal stream and the 
Virgo Overdensity. We examine the Sagittarius stream in the current LAMOST database, with 
particular focus on the low-latitude region near the Galactic anticenter, where LAMOST data are 
concentrated. Additionally, we look ahead to constraints that the full five-year LAMOST data will 
provide on the hierarchical merging history of the Milky Way. The survey will not only be 
valuable in characterizing the chemodynamics of known streams and tidal remnants of recent 
infalling satellites, but will provide a vast data set with which we can explore slightly older but 
still kinematically coherent remnants. We will discuss the prospects of this rich data set for 
recreating the merging history of the Milky Way over much of its lifetime.