Left: Radio and optical centroid positions (z_radio and z_opt; top), resulting radio-optical offset d_app (center, where the error bars correspond to the 1σ uncertainty on the centroid positions, estimated from the effective PSF widths), and apparent jet opening angle ${\theta }_{\mathrm{j}}^{\mathrm{app}}$ derived from the 43 GHz emission (bottom) shown as a function of jet power L_j for two stellar core radii r_c, s (see legend). The dashed line in the central panel represents the Gaia astrometrical precision. These results are obtained for a viewing angle θ_obs = 5°. The gray symbols indicate cases for which the corresponding centroid lies downstream of z(v = 0.9c) and are therefore excluded from the analysis. Right: Same as left but for a viewing angle θ_obs = 30°.