The value-added catalogue for LAMOST DR8 low-resolution spectra
  We present a value-added catalog containing stellar parameters estimated from
7.10 million low-resolution 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 $T_{\mathrm{eff}}$, surface gravity $\log g$,
metallicity [Fe/H]/[M/H]), $\alpha$-element to metal abundance ratio
[$\alpha$/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 $T_{\mathrm{eff}}$, $\log g$, [Fe/H], [M/H], [C/Fe],
[N/Fe] and [$\alpha$/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] $\sim -3.5$\,dex, significantly better than previous
results. The catalog provide 26,868 unique very metal poor star candidates
([Fe/H] $\leq -2.0$). 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.
