Bow-shocks and possible jet-shell interaction in the planetary nebula M 2-48

Deep narrow band CCD images in the Ha, [O III] λ5007 Å, [N II] λ6584 Å, and [S II] λ6717 + 31 Å emission lines have been obtained for the planetary nebula M 2-48. The discovery of a pair of symmetric low-excitation bow-shocks, separated by 4′, and forming a highly collimated bipolar outflow, is presented. The bow-shocks are emitting in [O III] and present the ionization structure expected from working surfaces of collimated jets, pointing out that these structures are tracing regions with shocked gas at high velocities (> 100 km s-1). In addition, an internal bipolar outflow (60″ × 30″) and an apparent off-center semi-circular shell (size ≈ 110″) are also detected. An enhancement of low-excitation line emission is observed in the shell along the outflow axis. This result can be interpreted in terms of a jet-shell interaction.