Comparison of the astrometric and spectroscopic radial velocities. Top: astrometric versus spectroscopic values for the sample shown as the dark blue histogram in Fig. 1 and colour-coded according to the formal uncertainty (σ_ρ) of the astrometric radial velocity estimate. The black line is the 1:1 relation. There are 28 data points that fall outside the limits ofthis plot. Bottom: difference between the astrometric and spectroscopic velocities for the sub-sample with σ_ρ < 10 km s⁻¹ (corresponding to Table 1), with error bars at ±σ_ρ. There are 11 data points outside of this plot.