LAMOST meets Gaia: The Galactic open clusters

Abstract

Open clusters (OCs) are born and evolve along the Milky Way (MW) plane. On them is imprinted the history of the Galactic disc, including its chemical and dynamical evolution. Chemical and dynamical properties of OCs can be derived from photometric, spectroscopic, and astrometric data of their member stars. Based on the photometric and astrometric data from the Gaia mission, the membership of stars in more than two thousand Galactic clusters has been identified in the literature. The chemical properties (e.g. metallicity) and kinematical properties (e.g. radial velocity), however, are still poorly known for many of these clusters. In synergy with the large spectroscopic survey LAMOST (data release 8) and Gaia (data release 2), we report a new comprehensive catalogue of 386 OCs. This catalogue has homogeneous parameter determinations of radial velocity, metallicity, and dynamical properties, such as orbit, eccentricity, angular momenta, total energy, and 3D Galactic velocity. These parameters enable the first radial velocity determination for 44 clusters, and the first spectroscopic [Fe/H] determination for 137 clusters. The metallicity distributions of the majority of clusters show falling trends in the parameter space of the Galactocentric radius, the total energy, and the Z component of angular momentum, except for two old groups that show flat tails in their own parameter planes. Cluster populations of ages younger and older than 500 Myr distribute diversely on the disc. The latter have a spatial consistency with the Galactic disc flare. The 3D spatial comparison between very young clusters (< 100 Myr) and nearby molecular clouds revealed a wide range of metallicity distribution along the Radcliffe gas cloud wave, indicating a possible inhomogeneous mixing or fast star formation along the wave. This catalogue will serve the community as a useful tool to trace the chemical and dynamical evolution of the MW.