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A. Loll, J.J. Hester (ASU), R. Sankrit, W. Blair (JHU)
We present the results of a Hubble Space Telescope WFPC2 imaging survey covering the entire Crab Nebula. The HST observations include eight fields imaged through F502N ([OIII]), F673N ([SII]), F631N ([OI]), and F547N (a relatively line-free continuum). The continuum filter reveals the synchrotron nebula, which is expanding into a much larger, freely expanding network of filaments comprised of ejecta from the explosion itself. The ejecta is heated and compressed due to a radiative shock, then cools and collects on the synchrotron nebula. These two plasmas are unstable to magnetic Rayleigh-Taylor instabilities, forming fingers that are quite distinctive in the images that will be presented. Where the R-T fingers exist, filamentary material is “poured in” from above causing the densest part of the fingers to be at the tip. In addition, the fingers are photoionized by the synchrotron continuum giving rise to very sharply stratified ionization structures. Neutral material can only survive at the dense center of the filaments. Surrounding this region are the low-ionization structures, namely O [I], which can be seen as bright, dense knots of emission. S[II] is also present but is more diffuse than O[I], yet the most diffuse emission in the extended regions of the Crab is made from the highly ionized O[III]. The combined, colored image shows the Crab filaments in unprecedented detail. The progressive development of Rayleigh-Taylor instabilities due to varying magnetic field strength, and systematic changes in the ionization structure are prominent. These HST images will be combined with ground-based spectroscopy to constrain the current photoionization model of these filaments to determine accurate abundances and densities within the nebula, arguably the most studied object in all of astrophysics. This work has been funded by a NASA Space Grant.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.