Exploring open cluster properties with Gaia and LAMOST

Abstract

Context. In Gaia DR2, an unprecedented high level of precision has been reached at sub-milliarcsecond for astrometry and millimagnitudes for photometry. Using cluster members identified with the astrometry and photometry in Gaia DR2, we can obtain a reliable determination of cluster properties. However, because of the shortcomings of Gaia spectroscopic observations in dealing with densely crowded cluster regions, the RVs and metallicity values for cluster member stars from Gaia DR2 are still lacking. It is necessary to combine the Gaia data with the data from large spectroscopic surveys, such as LAMOST, APOGEE, GALAH, and Gaia-ESO. Aims. In this study our aim is to improve the cluster properties by combining the LAMOST spectra. In particular, we provide the list of cluster members with spectroscopic parameters as an add-value catalog in LAMOST DR5, which can be used to perform a detailed study for a better understanding of the stellar properties, by using their spectra and fundamental properties from the host cluster. Methods. We cross-matched the spectroscopic catalog in LAMOST DR5 with the identified cluster members in Cantat-Gaudin et al. (2018, A&A, 618, A93). We then used members with spectroscopic parameters to derive statistical properties of open clusters. Results. We obtained a list of 8811 members with spectroscopic parameters and a catalog of 295 cluster properties. The provided cluster properties include astrometric parameters, spectroscopic parameters, derived kinematic and orbital parameters, and isochrone fitting results. In addition, we study the radial and vertical metallicity gradient and age-metallicity relation with the compiled open clusters as tracers, finding slopes of −0.053 ± 0.004 dex kpc−1, −0.252 ± 0.039 dex kpc−1, and 0.022 ± 0.008 dex Gyr−1, respectively. The slopes of the metallicity distribution relation for young clusters (0.1 Gyr < Age < 2 Gyr) and the age-metallicity relation for clusters within 6 Gyr are both consistent with the literature results. In order to fully study the chemical evolution history in the disk, more spectroscopic observations for old and distant open clusters are needed for further investigation.