Radial velocity comparison of Gaia DR2 and RAVE DR5 survey: A systematic offset in radial velocities among a group of highly accurate radial velocity stars

Abstract

Here, we report a comparative study of radial velocity (RV) data of two major surveys: Gaia Data Release 2 and RAVE Data Release 5. We restricted the sample to stars with relatively accurate RVs. The difference between RVGaia and RVRAVE for a majority of the sample follows a normal distribution with mean = 0.28 km s−1 and σ = 1.49 km s−1. However, we found a very small group of stars (≈0.08% of the total) for which the difference in RVs between the two surveys is significantly larger with an offset of −104.50 km s−1 with σ = 4.92 km s−1. Kinematics based on RVGaia suggest that most of the group members belong to the Galactic thin disk, which agrees with the group’s metallicity range of −1.2 to +0.5 dex suggesting the offset in RV is probably due to RAVE velocity data for this particular group.