Identification of Blue Horizontal-branch Stars from LAMOST DR5

Abstract

We construct a new catalog of the blue horizontal-branch (BHB) stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) DR5 data set, which contains 5355 + 81 BHB stars at high Galactic latitude (∣Glat∣ > 20°). We combine the spectral line indices with a set of Balmer line profile selection criteria to identify the BHB stars. During the selection process, we use the line index of Ca ii K to exclude the metal-rich A-type dwarfs. We obtain their atmospheric parameters by crossmatching our BHB stars with the catalog provided by Xiang et al. The results show that our sample is consistent with the theoretical T eff–log g evolutionary tracks of the BHB stars, indicating that our method is robust for identifying BHB stars from the LAMOST spectra. Their spatial distribution indicates that most of our BHB stars are located in the inner halo or the disk of the Milky Way. Combined with other BHB samples from the literature, the BHB stars can cover a large Galactic volume, which makes them a better probe for studying the kinematics, dynamics, and structural characteristics of the Milky Way.