Toomre diagrams of stars at 2–3r_d after a prograde minor merger (left), a retrograde minor merger (middle) and in a clumpy disk evolved in isolation for 3 Gyr. Plotted are the quadrature sum of vertical and radial velocities (u and w) as function of the rotational velocity, v, relative to the Local Standard of Rest. The primary galaxy in the merger models has a gas-to-stellar mass ratio of f_gas = 0.2. The dashed line marks a total velocity of 180 km s^-1, which serves as a potential criteria to separate thick disk stars and halo stars (Venn et al. 2004), and the dotted line is the Local Standard of Rest in these models. Also shown are the observed thick disk stars (triangles), halo stars with high α/Fe abundance (squares) and low α/Fe value (crosses) in the solar neighborhood, see Nissen & Schuster (2010) for further details. The halo stars in retrograde motion are shown in green whereas those in prograde motion are in blue.