Kinematic and chemical properties of five open clusters based on SDSS DR7

Abstract

We present metallicities and radial velocities for five old open clusters (NGC 6791, NGC 2420, NGC 2682, NGC 2158, and NGC 7789) using data from the seventh public data release of the Sloan Digital Sky Survey (SDSS), which includes the directed stellar program SEGUE: Sloan Extension For Galactic Understanding and Exploration. The radial velocities are used to calculate cluster membership probabilities for stars in each cluster region. NGC 6791, NGC 2420, NGC 2682, NGC 2158 and NGC 7789 are found to have mean metallicities [Fe/H] = +0.08 ± 0.09, −0.38 ± 0.11, −0.08 ± 0.05, −0.41 ± 0.13 and −0.19 ± 0.13 dex (s.d.), respectively. The mean radial velocities for NGC 6791, NGC 2420, NGC 2682, NGC 2158 and NGC 7789 are Vr = −45.9 ± 0.2, +76.1 ± 0.2, +35.0 ± 0.2, +26.9 ± 0.2 and −48.2 ± 0.2 km s−1(s.e.m.), respectively. We have compared our results with the values from literatures, and found that our metallicity of NGC 6791 is significantly underestimated (by about 0.3 dex) and our radial velocities of the open clusters agree well with the values derived using high-resolution spectroscopy.