Discovery of outlying high-velocity oxygen-rich ejecta in Cassiopeia A

Fesen, R. A., Hammell, M. C., Morse, J., Chevalier, R. A., Borkowski, K. J., Dopita, M. A., Gerardy, C. L., Lawrence, S. S., Raymond, J. C., van den Bergh, S. (January 2006) Discovery of outlying high-velocity oxygen-rich ejecta in Cassiopeia A. Astrophysical Journal, 636 (2). pp. 859-872. ISSN 0004-637X

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DOI: 10.1086/498092


Analysis of broadband HST ACS and WFPC2 images of the young Galactic supernova remnant Cassiopeia A reveals a far larger population of outlying, high-velocity knots of ejecta with a broader range of chemical properties than previously suspected. In this paper, we concentrate on a similar or equal to 1.5 arcmin(2) region located along the eastern limb of the remnant where we identify three main classes of outer ejecta: (1) knots dominated by [N(II)] lambda lambda 6548, 6583 emission, (2) knots dominated by oxygen emission lines, especially [O(II)] lambda lambda 7319, 7330, and (3) knots with emission-line strengths similar to the [S(II)]-strong fast-moving knot (FMK) ejecta commonly seen in the main emission shell. Mean transverse velocities derived from observed proper motion for N-rich, O-rich, and FMK-like knots identified in this region were found to be 8100, 7900, and 7600 km s(-1), respectively. The discovery of a significant population of O-rich ejecta situated between the suspected N-rich outer photospheric layer and S-rich FMK-like ejecta suggests that the progenitor's chemical layers were not completely disrupted by the supernova explosion outside of the remnant's northeast and southwest high-velocity "jet'' regions. In addition, we find the majority of O-rich outer ejecta at projected locations out beyond the remnant's fastest moving Fe-rich X-ray emission material seen in Chandra and XMM-Newton data along the eastern limb, suggesting that penetration of Fe-rich material up through the S-and Si-rich mantle did not extend past the progenitor's N- or O-rich outer layers for this section of the remnant.

Item Type: Paper
Uncontrolled Keywords: ISM : abundances ISM : individual (Cassiopeia A) ISM : kinematics and dynamics supernova remnants HUBBLE-SPACE-TELESCOPE SUPER-NOVA REMNANT X-RAY PRESUPERNOVA EVOLUTION PHYSICAL CONDITIONS ADVANCED CAMERA PROPER MOTIONS MASSIVE STARS EXPLOSION SPECTRA Astronomy & Astrophysics
Subjects: physics
CSHL Authors:
Communities: CSHL labs > Hammell M. lab
Depositing User: Matt Covey
Date: January 2006
Date Deposited: 06 Nov 2014 19:37
Last Modified: 06 Nov 2014 19:37

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