Distribution of the [Fe II] 1.644 μm emission along the jet. Left image: PV diagrams of [Fe II] 1.644 μm line in the Th 28 jet, obtained by coadding fluxes in the 16 spectral frames across the jet. Logarithmic contours are drawn from 10⁻¹⁴ erg s⁻¹ cm⁻² arcsec⁻² Å⁻¹, with an incremental logarithmic step of 0.3 dex. Two central panels: RV_peak and FWHM_in derived from fitting the PV diagram as a function of the distance from the source. The vertical line in the FWHM panel corresponds to 170 km s⁻¹ measured for the position of the source. Right four panels: Spectral profiles across the jet at selected position in the blue and red lobes (black points). The data was fit using a Moffat function (solid line). The intrinsic FWHM and the peak RV are shown at the top of each panel.