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Session 44 - New Light on Supernova Remnants.
Display session, Wednesday, June 11
South Main Hall,
N132D is one of two young, oxygen-rich supernova remnants in the LMC, and one of only eight known anywhere. Like their prototype, Cas A, all have filaments composed of nearly pure ejecta from core-collapse supernovae, which have not been decelerated or diluted through interactions with the ISM\@. A kinematic study of the oxygen-rich knots in N132D, using the CTIO 4m and imaging Fabry-Perot spectrograph, showed a roughly shell-like distribution, expanding at \sim1650 \ km\, s^-1, with a center of symmetry blue-shifted by \sim500 \ km\, s^-1\ with respect to the local medium (Morse, et al. 1995, AJ 109, 2104)\@.
We have now used the same telescope-instrument combination for a study of N132D in the much fainter coronal [Fe\thinspace XIV] line, \lambda\,5303\@. Since [Fe\thinspace XIV] arises from 10^6\ K plasma, its presence indicates material that has been recently excited by primary shocks. Not surprisingly, the [Fe\thinspace XIV] emission correlates well with soft X-ray maps of N132D, but our results have higher spatial resolution as well as being resolved in velocity space. The emission is distributed in two distinct regions: an outer horseshoe of [Fe\thinspace XIV] knots coincides closely with a system of bright but cooler knots seen in H\alpha\ and low-velocity [O\thinspace III], at rest relative to the local medium, and (2) a small inner ring of knots which do not appear prominently in other lines, and which are blue-shifted by \sim 300 \ km\, s^-1, almost the same as the center of symmetry of the fast [O\thinspace III] system. We suggest that the two regions indicate the positions of the blast wave and the reverse shock, respectively, both of which appear as limb-brightened shells at the different velocities. If this interpretation is correct, the inner [Fe\thinspace XIV] emission may indicate iron from the progenitor core that was mixed with other ejecta in the explosion.
This work has been supported by the NSF through grant AST-9315967 and by the W.M. Keck Foundation through the Keck Northeast Astronomy Consortium.
