Chandra Large Project Observations of the Supernova Remnant N132D: Measuring the Expansion of the Forward Shock

Abstract We present results from the Chandra X-ray Observatory Large Project (878 ks in 28 observations) of the Large Magellanic Cloud supernova remnant N132D. We measure the expansion of the forward shock in the bright southern rim to be <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0</mml:mn> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> <mml:mn>10</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0</mml:mn> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> <mml:mn>02</mml:mn> </mml:math> over the ∼14.5 yr baseline, which corresponds to a velocity of 1620 ± 400 km s −1 after accounting for several instrumental effects. We measure an expansion of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0</mml:mn> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> <mml:mn>23</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0</mml:mn> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> <mml:mn>02</mml:mn> </mml:math> and a shock velocity of 3840 ± 260 km s −1 for two features in an apparent blowout region in the northeast. The emission-measure-weighted average temperature inferred from X-ray spectral fits to regions in the southern rim is 0.95 ± 0.17 keV, consistent with the electron temperature implied by the shock velocity after accounting for Coulomb equilibration and adiabatic expansion. In contrast, the emission-measure-weighted average temperature for the northeast region is 0.77 ± 0.04 keV, which is significantly lower than the value inferred from the shock velocity. We fit 1D evolutionary models for the shock in the southern rim and northeast region, using the measured radius and propagation velocity into constant density and power-law profile circumstellar media. We find good agreement with the age of ∼2500 yr derived from optical expansion measurements for explosion energies of 1.5–3.0 × 10 51 erg, ejecta masses of 2–6 M ⊙ , and ambient medium densities of ∼0.33–0.66 amu cm −3 in the south and ∼0.01–0.02 amu cm −3 in the northeast assuming a constant density medium. These results are consistent with previous studies that suggested the progenitor of N132D was an energetic supernova that exploded into a preexisting cavity.