2000ApJ...544..889H

We report high-resolution (2".7x1".9) CO J=2-1 line imaging of the young planetary nebula M1-16 that reveals the shaping of its neutral envelope by collimated outflows or jets. An extended (∼50") envelope of molecular gas surrounds the compact (3") ionized nebula and dominates the mass of circumstellar material (∼0.12 M_☉). Multiple bipolar outflows, prominent at optical wavelengths, have pierced the envelope from the center, disrupting a significant fraction of the molecular gas. The outflows have excavated cavities along the bipolar axes, with CO velocities up to ∼30 km.s^–1 in the cavity walls, and have produced point-symmetric lobes of molecular gas by entrainment. These features, imprinted by the outflows on the neutral gas, will appear as characteristics of the ionized nebula as the envelope becomes more fully ionized. The outflow-envelope interactions seen in M1-16 exemplify the shaping mechanism of a wide class of planetary nebulae at early stages of their formation.