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K.J. Borkowski, B.J. Williams, S.P. Reynolds (NCSU), W.P. Blair, P. Ghavamian, R. Sankrit (JHU), S.P. Hendrick (Millersville Univ.), K.S. Long (STScI), S.D. Points, R.C. Smith (NOAO), J.C. Raymond (CfA), P.F. Winkler (Middlebury College)
Recent imaging and spectroscopic observations with the Spitzer Space Telescope have revealed thermal dust emission from a number of Galactic and Magellanic Clouds supernova remnants (SNRs). Emission in the 24 and 70 micron bands of the Multiband Imager and Photometer for Spitzer (MIPS) is particularly strong, while at the shorter wavelengths of the Infrared Array Camera (IRAC) dust emission is seen only in the most dense SNRs. Dust in SNRs is heated and destroyed in collisions with energetic particles present in X-ray emitting plasmas. Sputtering by energetic ions preferentially destroys small grains, modifying the original preshock grain size distribution. Infrared fluxes and spectra depend strongly on the plasma temperature and density, and they are sensitive to the grain size distribution because of the importance of stochastic heating of small grains by energetic particles. From Spitzer observations, we can learn about how dust is destroyed in SNRs and use IR spectra for plasma diagnostics, but this requires modeling of dust emission. We present collisionally-heated dust models for use with Spitzer observations of SNRs. Dust is modeled as a mixture of silicate and graphite grains with realistic grain size distributions, modified by sputtering, and with emission properties appropriate for relevant grain materials (including PAH emission from small carbonaceous grains). An enhancement of sputtering for small grains due to the small grain size (Jurac, Johnson, & Dunn 1998) is particularly important. We consider simple plane-parallel shock models as well as more realistic Sedov SNR models. Dust spectra and flux ratios in the IRAC and MIPS bands are presented for models with a wide range of preshock densities and shock speeds appropriate for present and future observations of SNRs by Spitzer.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.