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Near-Infrared Study of Iron Knots in Cassiopeia A Supernova Remnant

Published online by Cambridge University Press:  29 January 2014

Yong-Hyun Lee
Affiliation:
Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea email: yhlee@astro.snu.ac.kr, koo@astro.snu.ac.kr
Bon-Chul Koo
Affiliation:
Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea email: yhlee@astro.snu.ac.kr, koo@astro.snu.ac.kr
Dae-Sik Moon
Affiliation:
Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada email: moon@astro.utoronto.ca
Michael G. Burton
Affiliation:
School of Physics, University of New South Wales, Sydney, NSW 2052, Australia email: m.burton@unsw.edu.au
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Abstract

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We present the results of near-infrared (NIR) imaging and spectroscopic observations of the Galactic supernova remnant Cassiopeia A (Cas A). Applying the method of Principal Component Analysis to our broadband NIR spectra, we identify a total of 61 NIR emission knots of Cas A and classify them into three groups of distinct spectral characteristics: Helium-rich, Sulfur-rich, and Iron-rich groups. The first and second groups are of the circumstellar and supernova ejecta origin, respectively. The third group, which has enhanced iron emission, is of particular interests since it shows intermediate characteristics between the former two groups. We suggest that the Iron-rich group is knots of swept-up circumstellar medium around the contact discontinuity in Cas A and/or supernova ejecta from deep layers of its progenitor star which have recently encountered a reverse shock in the remnant.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2014 

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