Position–velocity diagrams of the [Fe ii] 1.644 μm emission line for five slit positions along the RW Aur jet (P.A. = 125°), co-added as described in the text. The velocity resolution is 20 km s ⁻¹ and the spatial resolution ~0.06 arcsec. Thin horizontal black lines in each frame show the spatial location of the star, and the arrow in the bottom right frame points to zero (heliocentric) velocity. Dashed vertical lines mark the velocities of the blueshifted and redshifted flows. Adjacent contours differ by a factor of two. There are no significant differences in the position–velocity diagrams for the different slit positions, which are sampled at roughly the Nyquist frequency of the instrumental resolution. The redshifted jet is brighter and slower than the blueshifted jet.