# LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC): the second release of value-added catalogues

## TL;DR

This paper releases the second version of a comprehensive stellar catalog from the LAMOST survey, providing detailed spectroscopic and photometric data for over 1.4 million stars to aid Galactic structure and evolution studies.

## Contribution

The paper introduces a new, extensive value-added catalog with improved stellar parameters, elemental abundances, and orbital data from the LSS-GAC survey, covering a large sky area.

## Key findings

- Radial velocity accuracy reaches 5 km/s for late-type stars.
- Distance estimates have 10-30% accuracy depending on S/N.
- Elemental abundance precisions are 0.1 dex for [Fe/H], 0.05 dex for [$
mf ext{alpha}$/Fe].

## Abstract

We present the second release of value-added catalogues of the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC DR2). The catalogues present values of radial velocity $V_{\rm r}$, atmospheric parameters --- effective temperature $T_{\rm eff}$, surface gravity log$g$, metallicity [Fe/H], $\alpha$-element to iron (metal) abundance ratio [$\alpha$/Fe] ([$\alpha$/M]), elemental abundances [C/H] and [N/H], and absolute magnitudes ${\rm M}_V$ and ${\rm M}_{K_{\rm s}}$ deduced from 1.8 million spectra of 1.4 million unique stars targeted by the LSS-GAC since September 2011 until June 2014. The catalogues also give values of interstellar reddening, distance and orbital parameters determined with a variety of techniques, as well as proper motions and multi-band photometry from the far-UV to the mid-IR collected from the literature and various surveys. Accuracies of radial velocities reach 5kms$^{-1}$ for late-type stars, and those of distance estimates range between 10 -- 30 per cent, depending on the spectral signal-to-noise ratios. Precisions of [Fe/H], [C/H] and [N/H] estimates reach 0.1dex, and those of [$\alpha$/Fe] and [$\alpha$/M] reach 0.05dex. The large number of stars, the contiguous sky coverage, the simple yet non-trivial target selection function and the robust estimates of stellar radial velocities and atmospheric parameters, distances and elemental abundances, make the catalogues a valuable data set to study the structure and evolution of the Galaxy, especially the solar-neighbourhood and the outer disk.