On the asymmetries of extended X-ray emission from planetary nebulae

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Title: On the asymmetries of extended X-ray emission from planetary nebulae
Author: Kastner, Joel; Li, Jingqiang; Vrtilek, Saeqa; Gatley, Ian; Merrill, K. Michael; Soker, Noam
Abstract: 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).
Description: Also archived in: arXiv: astro-ph/0202139 v2 30 Aug 2002
Record URI: http://hdl.handle.net/1850/1853
Date: 2002-12-20

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