The Three-Dimensional Structure of Cassiopeia A - Astrophysics > Astrophysics of GalaxiesReport as inadecuate

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Abstract: We used the Spitzer Space Telescope-s Infrared Spectrograph to map nearly theentire extent of Cassiopeia A between 5-40 micron. Using infrared and ChandraX-ray Doppler velocity measurements, along with the locations of optical ejectabeyond the forward shock, we constructed a 3-D model of the remnant. Thestructure of Cas A can be characterized into a spherical component, a tiltedthick disk, and multiple ejecta jets-pistons and optical fast-moving knots allpopulating the thick disk plane. The Bright Ring in Cas A identifies theintersection between the thick plane-pistons and a roughly spherical reverseshock. The ejecta pistons indicate a radial velocity gradient in the explosion.Some ejecta pistons are bipolar with oppositely-directed flows about theexpansion center while some ejecta pistons show no such symmetry. Some ejectapistons appear to maintain the integrity of the nuclear burning layers whileothers appear to have punched through the outer layers. The ejecta pistonsindicate a radial velocity gradient in the explosion. In 3-D, the Fe jet in thesoutheast occupies a -hole- in the Si-group emission and does not represent-overturning-, as previously thought. Although interaction with thecircumstellar medium affects the detailed appearance of the remnant and mayaffect the visibility of the southeast Fe jet, the bulk of the symmetries andasymmetries in Cas A are intrinsic to the explosion.

Author: Tracey DeLaney, Lawrence Rudnick, M. D. Stage, J. D. Smith, Karl Isensee, Jeonghee Rho, Glenn E. Allen, Haley Gomez, Takashi Koza


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