Member candidates of the star clusters from LAMOST DR2 data

TL;DR

This study identifies member candidates of 24 star clusters using LAMOST DR2 data through combined photometric and kinematic methods, evaluates the pipeline's parameter accuracy, and suggests prioritizing photometric candidates for future observations.

Contribution

It introduces a two-step membership identification process and assesses the accuracy of LAMOST pipeline parameters for star clusters.

Findings

Radial velocity data significantly aid membership identification.

Systematic offsets in radial velocity and metallicity are quantified.

Photometric candidates should be prioritized for follow-up observations.

Abstract

In this work, we provide 2189 photometric- and kinematic-selected member candidates of 24 star clusters from the LAMOST DR2 catalog. We perform two-step membership identification: selection along the stellar track in the color-magnitude diagram, i.e., photometric identification, and the selection from the distribution of radial velocities, i.e. the kinematic identification. We find that the radial velocity from the LAMOST data are very helpful in the membership identification. The mean probability of membership is 40\% for the radial velocity selected sample. With these 24 star clusters, we investigate the performance of the radial velocity and metallicity estimated in the LAMOST pipeline. We find that the systematic offset in radial velocity and metallicity are $0.85\pm1.26$\,\kms\ and $-0.08\pm0.04$\,dex, with dispersions of $5.47_{-0.71}^{+1.16}$\,\kms\ and $0.13_{-0.02}^{+0.04}$\,dex, respectively. Finally, we propose that the photometric member candidates of the clusters covered by the LAMOST footprints should be assigned higher priority so that more member stars can be observed.