Study on Sequoia Substructure Based on LAMOST postprint

Abstract: Sequoia is a retrograde substructure from the accretion event. This paper illus#2;trates the discovery, the criterion of member determination and the chemical properties of this substructure. Moreover, using the data information provided by LAMOST DR8 and Gaia, we compared the chemical abundance of Sequoia and GES according to the previous member star selection criteria. It was found that different selection criteria would affec#2;t the analysis to some extent, but there was no obvious boundary between the chemical abundances of Sequoia and GES. Meanwhile, we used the HDBSCAN clustering algorithm to select the kinematics of the clumps, further analyzed the chemical abundance of the clumps, and obtained a more obvious distribution of Sequoia than the previous comparison. However, we still could not clearly separate the Sequoia and GES from the chemical abundance using the abundance from low#2;resolution spectra. High resolution spectra data and more accurate selection criteria for further analysis are needed.