A sequence A,B,...S,T of simulated RVD models shown at distinct simulation instants with red lines. The models were obtained from the blue line RVD (evolved from the initial PDF in the Ψ_disk + Ψ_gas potential of total mass M_ref) by rescaling the horizontal and vertical directions so as to overlap with the black line reference RVD (from measurements) as good as possible. The blue line PDF does not differ much from the violet line PDF, which assumes β = 0. The light gray region is the RVD uncertainty defined by the vertical bars in Fig. 1. The bottom figure in each panel shows a β(r) profile corresponding to its respective RVD model. The decrease in β(r) towards negative values in the lower radii region r< 40 kpc is a model artifact discussed in the text.