Extended Structures of Planetary Nebulae Detected in H$_{2}$ Emission
  We present narrow-band near-infrared images of a sample of 11 Galactic
planetary nebulae (PNe) obtained in the molecular hydrogen (H$_{2}$) 2.122
$\mu$m and Br$\gamma$ 2.166 $\mu$m emission lines and the $K_{\rm c}$ 2.218
$\mu$m continuum. These images were collected with the Wide-field InfraRed
Camera (WIRCam) on the 3.6m Canada-France-Hawaii Telescope (CFHT); their
unprecedented depth and wide field of view allow us to find extended nebular
structures in H$_{2}$ emission in several PNe, some of these being the first
detection. The nebular morphologies in H$_{2}$ emission are studied in analogy
with the optical images, and indication on stellar wind interactions is
discussed. In particular, the complete structure of the highly asymmetric halo
in NGC6772 is witnessed in H$_{2}$, which strongly suggests interaction with
the interstellar medium. Our sample confirms the general correlation between
H$_{2}$ emission and the bipolarity of PNe. The knotty/filamentary fine
structures of the H$_{2}$ gas are resolved in the inner regions of several
ring-like PNe, also confirming the previous argument that H2 emission mostly
comes from knots/clumps embedded within fully ionized material at the
equatorial regions. Moreover, the deep H$_{2}$ image of the butterfly-shaped
Sh1-89, after removal of field stars, clearly reveals a tilted ring structure
at the waist. These high-quality CFHT images justify follow-up detailed
morpho-kinematic studies that are desired to deduce the true physical
structures of a few PNe in the sample.
