Three Moving Groups Detected in the LAMOST DR1 Archive

TL;DR

This study identifies three stellar moving groups in the LAMOST DR1 data, including two known and one newly discovered stream, providing insights into their origins and the Milky Way's dynamical history.

Contribution

The paper reports the detection of three moving groups in LAMOST DR1 data, including a new halo stream, and analyzes their formation mechanisms.

Findings

Identified three phase-space overdensities with >3 sigma significance.

Two streams are previously known, one is newly discovered.

Supports different origins for the streams, including debris from disrupted satellites.

Abstract

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 7,993 F, G and K nearby main-sequence stars (\textit{d} $<$ 2 kpc) with estimates of position (x, y, z) and space velocity ($U$, $V$, $W$) based on color and proper motion from the SDSS DR9 catalog. Three `phase-space overdensities' are identified in [\textit{V}, $\sqrt{U^{2}+2V^{2}}$] with significance levels of $\sigma$ $>$ 3. %[L$_{Z}$, eccentricity], [L$_{Z}$, L$_{\bot}$], and [V$_{az}$, V$_{\triangle}E$]. Two of them (Hyades-Pleiades stream, Arcturus-AF06 stream) have been identified previously. We also find evidence for a new stream (centered at \textit{V} $\sim$ -180 km s$^{-1}$) in the halo. The formation mechanisms of these three streams are analyzed. Our results support the hypothesis the Arcturus-AF06 stream and the new stream originated from the debris of a disrupted satellite, while Hyades-Pleiades stream has a dynamical origin.