2018ApJ...859...92F

We present narrowband near-infrared images of a sample of 11 Galactic planetary nebulae (PNe) obtained in the H₂ 2.122 µm and Brγ 2.166 µm emission lines and the K_c 2.218 µm continuum. These images were collected with the Wide-field Infrared Camera on the 3.6 m Canada-France-Hawaii Telescope (CFHT); their unprecedented depth and wide field of view allow us to find extended nebular structures in H₂ emission in several PNe, some of these being the first detection. The nebular morphologies in H₂ emission are studied in analogy with the optical images, and indication of stellar wind interactions is discussed. In particular, the complete structure of the highly asymmetric halo in NGC 6772 is witnessed in H₂, which strongly suggests interaction with the interstellar medium. Our sample confirms the general correlation between H₂ emission and the bipolarity of PNe. The knotty or filamentary fine structures of the H₂ gas are resolved in the inner regions of several ring-like PNe, also confirming the previous argument that H₂ emission mostly comes from knots or clumps embedded within fully ionized material at the equatorial regions. Moreover, the H₂ image of the butterfly-shaped Sh 1-89, after removal of field stars, clearly reveals a tilted ring structure at the waist. These high-quality CFHT images justify follow-up detailed morphokinematic studies that are desired in order to deduce the true physical structures of a few PNe in the sample.