Chandra Legacy Observation of the LMC SNR N132D: Expansion of the Forward Shock

We present results from a deep (900 ks) observation of the Large Magellanic Cloud supernova remnant N132D with the Chandra X-ray Observatory. N132D is an O-rich supernova remnant (SNR) of a 15-25 Mdot progenitor and is the most X-ray luminous SNR in the Local Group (L_x~1.0x10³⁸ ergs/s [0.3-10.0 keV]). The Chandra images reveal the spatial distribution of the elements Ne, Mg, Si, S, and Fe in unprecedented detail and a bright rim in the south where the shock is interacting with a molecular cloud complex. We have compared the images of the bright rim from Chandra observations in 2006 to our new data to derive an expansion of 0.112 ± 0.024 arcsec over the 14.15 yr baseline which corresponds to a shock velocity of 1877 ± 402 km/s. We measure a shock velocity of 3503 ± 255 km/s for a feature in an apparent blowout region in the north-east and use this value to estimate the deceleration of the shock wave in the molecular cloud interaction region. Spectral fits to narrow regions near the shock front result in an electron temperature of T_e~1.00 keV assuming a non-equilibrium ionization model with abundances typical of the interstellar medium in the LMC. This electron temperature implies a shock velocity of ~855 km/s assuming full electron-ion equilibration. We explore whether this apparent discrepancy between the electron temperature inferred from the measured shock velocity and that inferred from the spectral fits may be explained by cooling from Coulomb collisions and adiabatic expansion within the spectral extraction region.