The value-added catalogue for LAMOST DR8 low-resolution spectra

Abstract

We present a value-added catalog containing stellar parameters estimated from 7.10 million lowresolution spectra for 5.16 million unique stars with spectral signal-to-noise ratios (SNRs) higher than 10 obtained by the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Galactic spectroscopic surveys. The catalog presents values of stellar atmospheric parameters (effective temperature T eff , surface gravity log g, metallicity [Fe/H]/[M/H]), α-element to metal abundance ratio [α/M], carbon and nitrogen to iron abundance ratios [C/Fe] and [N/Fe] and 14 bands' absolute magnitudes deduced from LAMOST spectra using the method of neural network. The spectro-photometric distances of those stars are also provided based on the distance modulus. For stars with spectral SNRs larger than 50, precisions of T eff , log g, [Fe/H], [M/H], [C/Fe], [N/Fe] and [α/M] are 85 K, 0.098 dex, 0.05 dex, 0.05 dex, 0.052 dex, 0.082 dex and 0.027 dex, respectively. The errors of 14 band's absolute magnitudes are 0.16-0.22 mag for stars with spectral SNRs larger than 50. The spectro-photometric distance is accurate to 8.5% for stars with spectral SNRs larger than 50, and is more accurate than geometrical distance for stars with distance larger than 2.0 kpc. Our estimates of [Fe/H] are reliable down to [Fe/H] ∼ −3.5 dex, significantly better than previous results. The catalog provide 26,868 unique very metal poor star candidates ([Fe/H] ≤ −2.0). The catalog would be a valuable data set to study the structure and evolution of the Galaxy, especially the solar-neighbourhood and the outer disc.