Three Moving Groups Detected in the LAMOST DR1 Archive

We analyze the kinematics of thick disk and halo stars observed by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope. We have constructed a sample of 7993 F, G, and K nearby main-sequence stars ( d < 2 kpc) with estimates of position ( x , y , z ) and space velocity ( U , V , W ) based on color and proper motion from the Sloan Digital Sky Survey DR9 catalog. Three “phase-space overdensities” are identified in ( V ,√ U 2 + 2 V 2) with significance levels of σ > 3. Two of them (the Hyades–Pleiades stream and the Arcturus–AF06 stream) have been identified previously. We also find evidence for a new stream (centered at V ∼ −180 km s−1) in the halo. The formation mechanisms of these three streams are analyzed. Our results support the hypothesis that the Arcturus–AF06 stream and the new stream originated from the debris of a disrupted satellite, while the Hyades–Pleiades stream has a dynamical origin.