Optical Structure and Proper‐Motion Age of the Oxygen‐rich Supernova Remnant 1E 0102−7219 in the Small Magellanic Cloud

We present new optical emission-line images of the young SNR 1E 0102-7219(E0102) in the SMC obtained with the HST Advanced Camera for Surveys (ACS).E0102 is a member of the oxygen-rich class of SNRs showing strong oxygen, neon, and other metal-line emissions in its optical and X-ray spectra, and anabsence of H and He. The progenitor of E0102 may have been a Wolf-Rayet starthat underwent considerable mass loss prior to exploding as a Type Ib/c orIIL/b SN. The ejecta in this SNR are fast-moving (V > 1000 km/s) and emit asthey are compressed and heated in the reverse shock. In 2003, we obtainedoptical [O III], H-alpha, and continuum images with the ACS Wide Field Camera.The [O III] image captures the full velocity range of the ejecta, and showsconsiderable high-velocity emission projected in the middle of the SNR that wasDoppler-shifted out of the narrow F502N bandpass of a previous Wide Field andPlanetary Camera 2 image from 1995. Using these two epochs separated by ~8.5years, we measure the transverse expansion of the ejecta around the outer rimin this SNR for the first time at visible wavelengths. From proper-motionmeasurements of 12 ejecta filaments, we estimate a mean expansion velocity forthe bright ejecta of ~2000 km/s and an inferred kinematic age for the SNR of\~2050 +/- 600 years. The age we derive from HST data is about twice thatinferred by Hughes et al.(2000) from X-ray data, though our 1-sigma error barsoverlap. Our proper-motion age is consistent with an independent opticalkinematic age derived by Eriksen et al.(2003) using spatially resolved [O III]radial-velocity data. We derive an expansion center that lies very close toX-ray and radio hotspots, which could indicate the presence of a compactremnant (neutron star or black hole).