Core-shift vectors and core-shift power-law fits for each calibrator. Left: self-referencing core-shift vectors in polar grids. The dotted lines are given at intervals of 30 degrees. (a) J0006: all vectors consistently point in the jet direction towards the east (see Fig. B.1). (c) J0007: CX, XU, and the mean vectors consistently point in the jet direction towards the north, while the UK vector points towards the north-west (see Fig. B.2). (e) J0008: only the CX and the mean vector consistently point in the jet direction towards the south-east (see Fig. B.3). Right: core shift (Δr) as a function of frequency (ν_GHz). The red curve indicates the best fit of the form: with the K-band as the reference frequency. The blue and green curves indicate the fits when the power-law index k_r is set to 1 with the fitting function: . The constants a and b are fitting parameters. (b) J0006: the best fitting curve gives a = 5.8 ± 1.4 and k_r = 0.72 ± 0.08. The fit with k_r = 1 gives b = 3.3 ± 0.2. (d) J0007: the best fitting curve gives a = 5.04 ± 1.61 and k_r = 0.71 ± 0.11. The fit with k_r = 1 gives b = 2.8 ± 0.2. (f) J0008: the best fitting curve gives a = 31.7 ± 38.8 and k_r = 0.33 ± 0.09. Without the U-band, the fit with k_r = 1 gives b = 1.2 ± 0.4.