  Chandra X-ray Observatory (CXO) images have revealed that the X-ray emitting
regions of the molecule-rich young planetary nebulae (PNs) BD+30 3639 (BD+30)
and NGC 7027 are much more asymmetric than their optical nebulosities. To
evaluate the potential origins of these X-ray asymmetries, we analyze X-ray
images of BD+30, NGC 7027, and another planetary nebula resolved by CXO, NGC
6543, within specific energy bands. Image resolution has been optimized by
sub-pixel repositioning of individual X-ray events. The resulting
subarcsecond-resolution images reveal that the soft (E < 0.7 keV) X-ray
emission from BD+30 is more uniform than the harder emission, which is largely
confined to the eastern rim of the optical nebula. In contrast, soft X-rays
from NGC 7027 are highly localized and this PN is more axially symmetric in
harder emission. The broad-band X-ray morphologies of BD+30 and NGC 7027 are
highly anticorrelated with their distributions of visual extinction, as
determined from high-resolution, space- and ground-based optical and infrared
imaging. Hence, it is likely that the observed X-ray asymmetries of these
nebulae are due in large part to the effects of nonuniform intranebular
extinction. However, the energy-dependent X-ray structures in both nebulae and
in NGC 6543 -- which is by far the least dusty and molecule-rich of the three
PNs, and displays very uniform intranebular extinction -- suggests that other
mechanisms, such as the action of collimated outflows and heat conduction, are
also important in determining the detailed X-ray morphologies of young
planetary nebulae.
