Three-dimensional magnetohydrodynamical modeling of planetary nebulae: The formation of jets, ansae, and point-symmetric nebulae via magnetic collimation

Three-dimensional, magnetohydrodynamical simulations of the formation and evolution of planetary nebulae are discussed, and we confirm that planetary nebula jets and ansae can be obtained by magnetic collimation of their central, post-asymptotic giant branch, fast winds. Jets and ansae form at the polar regions as a result of the magnetic tension produced by the magnetized winds. Exterior density distributions anisotropic with latitude (e.g., accretion disks, wind-compressed disks, etc.) are not required inside this framework. We find that the expansion velocity of the jets and ansae coincides with the wind velocity of the post-asymptotic giant branch phase. We propose that the formation of ''attached'' and ''detached'' ansae involves, as a simplified model, two and three winds, respectively. We also show that the formation of rotating jets and point-symmetric nebular shapes can be the result of magnetic collimation around a precessing star. If the precession is caused by a tidal force, only a wide binary system is required.