Tracing the Origin of Moving Groups. II. Chemical Abundance of Six Stars in the Halo Stream LAMOST-N1

Abstract

Abstract We present the chemical abundances of six stars in the halo stream Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST)-N1, a new kinematically selected substructure from LAMOST data, from high-resolution spectra obtained with the Subaru/High Dispersion Spectrograph. Atmospheric parameters were determined by an iterative procedure based on spectroscopic analysis. Abundances of 11 elements, including α elements (Mg, Ca, Ti), odd-Z light elements (Na), iron-peak elements (Sc, Cr, Mn, Fe, Ni), and neutron-capture elements (Y, Ba), are measured by local thermodynamic equilibrium analysis procedures. [Fe/H] of the six stars ranges from −1.5 to −0.66. The abundance patterns of α elements show a similar trend to those of low-α stars in Nissen et al. and over 0.1 dex lower than those of Galactic field stars. The Sc, Cr, Mn, and Ni abundances of these six stars exhibit a positive trend with increasing iron abundance, with varying gradients. In addition, abundance distribution between [Na/Fe] and [Ni/Fe] and between that of [Ba/Y] and [Fe/H] of these six stars is different from both Galactic stars and the known dwarf galaxies. Our results suggest that LAMOST-N1 might be a relic of a system with slower chemical evolutions than the Milky Way.