LAMOST VMP MSTO and red giant star metallicities

More than 7000 of these candidates are brighter than G~16, making them excellent targets for high-resolution spectroscopic follow-up with 4-10m class telescopes. Unlike most previous studies, we employed an empirical calibration to estimate metallicities from the equivalent widths of the calcium triplet lines, taking advantage of the high signal-to-noise ratio in the red arm of LAMOST spectra.

We further refined this calibration to improve its reliability for more distant stars. This method enables robust identification of VMP candidates with metallicities as low as [Fe/H]=-4.0 among both MSTO and red giant stars. Comparisons with metal-poor samples from other spectroscopic surveys and high-resolution follow-up observations confirm the accuracy of our estimates, showing a typical median offset of ~0.1dex and a standard deviation of ~0.2dex.