We present a three-dimensional kinematic reconstruction of the optically-emitting , oxygen-rich ejecta of supernova remnant N132D in the Large Magellanic Cloud .
Data were obtained with the 6.5 m Magellan telescope in combination with the IMACS+GISMO instrument and survey [ O III ] \lambda \lambda 4959 , 5007 line emission in a { \sim } 3 ^ { \prime } ~ { } \times 3 ^ { \prime } region centered on N132D .
The spatial and spectral resolution of our data enable detailed examination of the optical ejecta structure .
The majority of N132D ’ s optically bright oxygen ejecta are arranged in a torus-like geometry tilted approximately 28 ^ { \circ } with respect to the plane of the sky .
The torus has a radius of 4.4 pc ( D _ { LMC } /50 kpc ) , exhibits a blue-shifted radial velocity asymmetry of -3000 to +2300 km s ^ { -1 } , and has a conspicuous break in its circumference .
Assuming homologous expansion from the geometric center of O-rich filaments , the average expansion velocity of 1745 km s ^ { -1 } translates to an age since explosion of 2450 \pm 195 yr. A faint , spatially-separated “ runaway knot ” ( RK ) with total space velocity of 3650 km s ^ { -1 } is nearly perpendicular to the torus plane and coincident with X-ray emission that is substantially enhanced in Si relative to the LMC and N132D ’ s bulk ejecta .
These kinematic and chemical signatures suggest that the RK may have had its origin deep within the progenitor star .
Overall , the main shell morphology and high-velocity , Si-enriched components of N132D have remarkable similarity with that of Cassiopeia A , which was the result of a Type IIb supernova explosion .
Our results underscore the need for further observations and simulations that can robustly reconcile whether the observed morphology is dominated by explosion dynamics or shaped by interaction with the environment .