We analyze the dynamical properties of ?1500 very metal-poor (VMP; [Fe/H] ? ?2.0) halo stars, based primarily on medium-resolution spectroscopic data from HK and Hamburg/ESO surveys. These data, collected over past 30 yr, are supplemented by a number calibration stars other small samples, along with astrometric information Gaia DR2. apply clustering algorithm to 4D energy-action space sample, i...
