Photocentre shift for [Fe II] 1.534, 1.644 μm, Paβ, Brγ, and H₂ 2.122, 2.406 μm along the XY-directions. The Y-direction is aligned with the jet axis, whereas the X-direction is orthogonal. The wavelength of spectral lines in the vacuum is indicated by vertical lines. On some plots, the values of centre coordinates are shifted as a whole in order to place both distributions on the same plot. The instrumental bias around Brγ, calculated from the continuum, was fit with a linear function (shown as dashed lines) and removed from further analysis. The shifts in the line cores were corrected for the line-to-continuum ratio, and the errors derived for the line centre displacement are shown. All the emission lines display a significant photocentre shift along the Y-direction (the direction of the jet), whereas the H₂ lines also show a small shift in the orthogonal direction (X).