Spitzer spectral mapping of supernova remnant Cassiopeia A
Abstract
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 ~ 10^4 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, highenergy 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.
Additional Information
© 2009 The American Astronomical Society. Received 2008 August 1; accepted 2008 October 15; published 2009 March 3. The authors thank D. Arnett for helpful discussion, and an anonymous referee for useful comments which improved this manuscript. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA/ JPL through award 1264030.Attached Files
Published - Smith2009p63710.10880004-637X6931713.pdf
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Additional details
- Eprint ID
- 14712
- Resolver ID
- CaltechAUTHORS:20090729-082847156
- 1264030
- JPL
- 1407
- NASA
- Created
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2009-08-12Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field