Balmer Arcs in HH 47

A detailed view of the region including the [S II]-bright knots A_{22} and A_{26} and the H-alpha-bright filaments associated with them: (a) H-alpha; (b) [S II]; (c) H-alpha minus [S II]; (d) a cartoon showing the possible locations of the shock fronts and their motion. The regions marked 'FAST' and 'SLOW' were determined from radial velocity measurements of the emission lines.