The Arcturus moving group

Abstract

The Arcturus moving group is a well-populated example of phase space substructure within the disk of our Galaxy. With its large rotational lag (V = -100 km/s{u207B}{u00B9}), metal poor nature ([Fe/H] ~ -0.6) and significant age (10 Gyr) it belongs to the Galaxy's thick disk. Traditionally regarded as the remains of a dissolved open cluster, it has recently been suggested to be a remnant of a satellite accreted by our Galaxy. We undertook a high-resolution spectroscopic abundance study of Arcturus group members and candidates to understand the origin of the group. Examining abundance of Fe, Mg, Ca, Ti, Cr, Ni, Zn, Ce, Nd, Sm and Gd for 134 stars we found the surprising result that the group is chemically similar to thick (and some thin) disk stars. After confirming the existence of the group via further kinematic studies using the Nordstr{u00F6}m et al. (2004), Schuster et al. (2006) and RAdial Velocity Experiment (RAVE) surveys (Steinmetz et al., 2006), we conclude that the group is most likely the result of a resonance with the bar of the Galaxy. This dynamical origin is consistent with our abundance results as well as the kinematical and spatial dependencies that the group exhibits. These results are motivation for further study to understand the dynamics involved in resonant behaviour with the Galaxy's bar. Show more