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B.J. Williams, K.J. Borkowski, S.P. Reynolds (North Carolina State Univ.), W.P. Blair, P. Ghavamian, R. Sankrit (Johns Hopkins Univ.), S. Hendrick (Millersville Univ.), P.F. Winkler (Middlebury College), R.C. Smith, S. Points (NOAO), J. Raymond (CfA), K. Long (STScI)
We present results from an extensive survey of supernova remnants (SNRs) in the Magellanic Clouds using the Spitzer Space Telescope. We have obtained IR images in both IRAC and MIPS bands for several dozen SNRs in the clouds, with detection in at least 17 SNRs arising from both core-collapse and type Ia SNe. Emission from SNRs in the IR is dominated by thermal emission from dust grains. Comparison of IR-detected remnants with available Chandra broadband and optical images shows a clear association with the blast wave, and not with interior X-ray emission associated with the SN ejecta. We infer from this that we are seeing ambient interstellar dust heated by the plasma in the shock wave, and not dust formed in the SN ejecta. We model grain emission using inferred plasma densities and temperatures of the X-ray emitting gas, and we include the destruction (sputtering) of grains by energetic ions. These models and observed Spitzer relative IR fluxes are consistent with the sputtering of dust grains by at least several nanometers, destroying small grains, which would produce more short-wavelength IR emission than observed. For example, in DEM L71, without sputtering, 70/24 micron flux ratios are too small by factors of order 2. Flux measurements at 24 microns also provide a measure of the total mass of dust in the SNR. Our results for DEM L71 underpredict the amount of dust found in SNRs, based on estimates of the average dust/gas mass ratio in the MCs. In DEM L71, we find a total dust mass of about 0.05 solar masses, whereas predictions are about 0.3. We will present dust mass measurements and upper limits from our other detected remnants as well.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.