Spitzer IRAC Images and Sample Spectra of Cassiopeia A's Explosion

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dc.creatorEnnis, J. A.
dc.creatorRudnick, L.
dc.creatorReach, W. T.
dc.creatorSmith, J. D.
dc.creatorRho, J.
dc.creatorDeLaney, T.
dc.creatorGomez, H.
dc.creatorKozasa, T.
dc.date2006-10-27
dc.date2006-11-01
dc.date.accessioned2026-07-07T11:57:27Z
dc.date.available2026-07-07T11:57:27Z
dc.descriptionWe present Spitzer IRAC images, along with representative 5.27 to 38.5 micron IRS spectra of the Cassiopeia A supernova remnant. We find that various IRAC channels are each most sensitive to a different spectral and physical component. Channel 1 (3.6 micron) matches radio synchrotron images. Where Channel 1 is strong with respect to the other channels, the longer-wavelength spectra show a broad continuum gently peaking around 26 micron, with weak or no lines. We suggest that this is due to un-enriched progenitor circumstellar dust behind the outer shock, processed by shock photons and electrons. Where Channel 4 (8 micron) is bright relative to the other IRAC channels, the long-wavelength spectra show a strong, 2-3 micron-wide peak at 21 micron, likely due to silicates and proto-silicates, as well as strong ionic lines of [Ar II], [Ar III], [S IV] and [Ne II]. In these locations, the dust and ionic emission originate from the explosion's O-burning layers. The regions where Channels 2 (4.5 micron) and 3 (5.6 micron) are strongest relative to Channel 4 show a spectrum that rises gradually to 21 micron, and then flattens or rises more slowly to longer wavelengths, along with higher ratios of [Ne II] to [Ar II]. Dust and ionic emission in these locations arise primarily from the C- and Ne- burning layers. These findings are consistent with asymmetries in the explosion producing variations in the velocity structure in different directions, but preserving the nucleosynthetic layers. At each location, the dust and ionic lines in the mid-infrared, and the hotter and more highly ionized optical and X-ray emission are then dominated by the layer currently encountering the reverse shock in that direction.
dc.description28 pages, 10 figures, accepted in to the Astrophysical Journal. For full-resolution images, please see http://webusers.astro.umn.edu/~jennis/iracpaper.html. Revised to correct an error in references
dc.identifierhttps://arxiv.org/abs/astro-ph/0610838
dc.identifierhttp://arxiv.org/abs/astro-ph/0610838
dc.identifierAstrophys.J.652:376-386,2006
dc.identifierdoi:10.1086/508142
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/205890
dc.subjectAstrophysics
dc.titleSpitzer IRAC Images and Sample Spectra of Cassiopeia A's Explosion
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