On the Symmetries of Extended X-Ray Emission from Planetary Nebulae
This is the pre-print of an article published by the American Astronomical Society. The final, published version is available here: https://doi.org/10.1086/344363
© 2002 The American Astronomical Society
Also archived in: arXiv: astro-ph/0202139 v2 30 Aug 2002
The authors wish to thank two anonymous referees for many helpful comments and suggestions. J.H.K. and J.L. acknowledge support for this research provided by NASA/CXO grant GO0–1067X to RIT. N.S. acknowledges support from the US-Israel Binational Science Foundation.
Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.
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 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◦3639, 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◦3639 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◦3639 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 (Refer to PDF file for exact formulas).