Element Abundance Analysis of the Metal-rich Stellar Halo and High-velocity Thick Disk in the Galaxy

Abstract

Based on the second Gaia data release (DR2) and APOGEE (DR16) spectroscopic surveys, we define two kinds of star samples: high-velocity thick disk (HVTD) with v_φ > 90 km s^-1 and metal-rich stellar halo (MRSH) with v_φ < 90 km s^-1. Due to high-resolution spectra data from APOGEE (DR16), we can accurately analyze the element abundance distribution of HVTD and MRSH. These element abundances constitute a multidimensional data space, and we introduce an algorithm method for processing multidimensional data to give the result of dimensionality reduction clustering. According to chemical property analysis, we derive that some HVTD stars could originate from the thin disk and some MRSH stars could originate from dwarf galaxies, but those stars that have similar chemical abundance characteristics in both samples may form in situ.