H₂ S(6) and its second-order ghost toward HH 168. (a) S(6) map, convolved to the 0﹩\mathop{.}\limits^{^{\prime\prime} }﹩51 resolution of (b). (b) U12217 map, with S(6) contours (20%–80% of peak) and the Channel 1B field of view (dotted). (c) Continuum-subtracted spectra: S(6) (black, offset by +400 mJy) and U12217 (×30, plotted at half its wavelength); vertical lines mark the velocity centroids of S(6) (black, dotted) and U12217 (red, solid).