Toomre diagram of GCS stars. Left and middle panels: the thin/thick disk decomposition of GCS stars was performed using the velocity dispersions and star fractions from Soubiran et al. (2003) (left) and from Robin et al. (2003) (middle). The thin, thick, and intermediate stars of the GCS are represented by green dots, red stars, and open blue circles, respectively. The dashed lines indicate the total space velocity, , in steps of 50 km s^-1. Right panel: Toomre diagram showing the groups identified by Famaey et al. (2005): the Hercules stream (red open triangles), high-velocity stars (blue open diamonds), and B-group stars (green open circles). In all panels the present sample is indicated by black dots.