A Metallicity Catalog of Very Metal-poor Main-sequence Turn-off and Red Giant Stars from LAMOST DR10

TL;DR

This paper introduces a catalog of over 8,400 very metal-poor stars from LAMOST DR10, using an empirical calibration of Calcium Triplet lines to estimate metallicities, facilitating the identification of extremely metal-poor stars for follow-up studies.

Contribution

The study develops a new empirical calibration method for metallicity estimation from low-resolution spectra, enabling reliable identification of stars with [Fe/H] as low as -4.0.

Findings

Successfully identified 8,440 VMP star candidates.

Calibration achieves ~0.1 dex median offset in metallicity estimates.

Over 7,000 candidates are suitable for high-resolution follow-up.

Abstract

We present a catalog of 8,440 candidate very metal-poor (VMP; [Fe/H] < -2.0) main-sequence turn-off (MSTO) and red giant stars in the Milky Way, identified from low-resolution spectra in LAMOST DR10. More than 7,000 of these candidates are brighter than G ~ 16, making them excellent targets for high-resolution spectroscopic follow-up with 4-10 meter-class telescopes. Unlike most previous studies, we employed an empirical calibration to estimate metallicities from the equivalent widths (EWs) of the Calcium Triplet (CaT) lines, taking advantage of the high signal-to-noise ratio (SNR) 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 ~0.1 dex and a standard deviation of ~0.2 dex.