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Spitzer spectral mapping of supernova remnant Cassiopeia A

Smith, J. D. T., Rudnick, Lawrence, Delaney, Tracey, Rho, Jeonghee, Gomez, Haley Louise, Kozasa, Takashi, Reach, William and Isensee, Karl 2009. Spitzer spectral mapping of supernova remnant Cassiopeia A. Astrophysical Journal 693 (1) , pp. 713-721. 10.1088/0004-637X/693/1/713

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We present the global distribution of fine-structure infrared line emission in the Cassiopeia A supernova remnant using data from the Spitzer Space Telescope's infrared spectrograph. We identify emission from ejecta materials in the interior, prior to their encounter with the reverse shock, as well as from the postshock bright ring. The global electron density increases by 100 at the shock to ~104 cm–3, providing evidence for strong radiative cooling. There is also a dramatic change in ionization state at the shock, with the fading of emission from low-ionization interior species like [Si II] giving way to [S IV] and, at even further distances, high-energy X-rays from hydrogenic silicon. Two compact, crescent-shaped clumps with highly enhanced neon abundance are arranged symmetrically around the central neutron star. These neon crescents are very closely aligned with the "kick" direction of the compact object from the remnant's expansion center, tracing a new axis of explosion asymmetry. They indicate that much of the apparent macroscopic elemental mixing may arise from different compositional layers of ejecta now passing through the reverse shock along different directions.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: infrared: general; supernova remnants; supernovae: individual (Cassiopeia A); X-rays: ISM
Publisher: IOP Publishing
ISSN: 0004-637X
Last Modified: 04 Jun 2017 03:31

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