Nucleosynthetic Layers in the Shocked Ejecta of Cassiopeia A

Abstract

We present a 3-dimensional analysis of the supernova remnant Cassiopeia A using high resolution spectra from the Spitzer Space Telescope. We observe supernova ejecta both immediately before and during the shock-ejecta interaction. We determine that the reverse shock of the remnant is spherical to within 7%, although the center of this sphere is offset from the geometric center of the remnant by 810 km/s. We determine that the velocity width of the nucleosynthetic layers is approximately 1000 km/s over 4000 square arcsecond regions, although the velocity width of a layer along any individual line of sight is <250 km/s. Si and O, which come from different nucleosynthetic layers in the progenitor star, are observed to be coincident in velocity space in some directions, but segregated by up to approximately 500 km/s in other directions. We compare these observations of the nucleosynthetic layers to predictions from supernova explosion models in an attempt to constrain such models. Finally, we observe small-scale, corrugated velocity structures that are likely caused during the supernova explosion itself, rather than hundreds of years later by dynamical instabilities at the remnant's reverse shock.

31 pages, 14 figures, ApJ, in press

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• The chemically controlled synthesis of dust in type II-P supernovae
• Interstellar and Ejecta Dust in the Cas A Supernova Remnant
• New Galactic supernova remnants discovered with IPHAS
• Molecules and dust in Cassiopeia A: II - Dust sputtering and diagnosis of dust survival in supernova remnants
• Element Abundances in the Unshocked Ejecta of Cassiopeia A
• Interaction between Cassiopeia A and Nearby Molecular Clouds
• A Deep Near-Infrared [Fe II]+[Si I] Emission Line Image of the Supernova Remnant Cassiopeia A
• The Temperature and Ionization of Unshocked Ejecta in Cas A
• Near-infrared Extinction due to Cool Supernova Dust in Cassiopeia A
• A Decade-Baseline Study of the Plasma States of Ejecta Knots in Cassiopeia A
• X-ray Studies of the Inverted Ejecta Layers in the Southeast Area of Cassiopeia A
• Far-infrared Polarization of the Supernova Remnant Cassiopeia A with SOFIA HAWC+
• Decadal brightening in the northeastern non-thermal filament of Cassiopeia A