Filaments as Possible Signatures of Magnetic Field Structure in Planetary Nebulae

We draw attention to the extreme filamentary structures seen inhigh-resolution optical images of certain planetary nebulae. We determine thephysical properties of the filaments in the nebulae IC 418, NGC 3132, and NGC6537, and based on their large length-to-width ratios, longitudinal coherence,and morphology, we suggest that they may be signatures of the underlyingmagnetic field. The fields needed for the coherence of the filaments areprobably consistent with those measured in the precursor circumstellarenvelopes. The filaments suggest that magnetic fields in planetary nebulae mayhave a localized and thread-like geometry.