[Fe XIV] and [Fe XI] reveal the forward shock in SNR 1E 0102.2-7219

Aims. We study the forward shock in the oxygen-rich young supernova remnant (SNR) 1E 0102.2-7219 (1E 0102 in short) via optical coronal emission from [Fe XIV] and [Fe XI]: Emission lines that allow for the use of an alternative method to X-rays for this purpose. Methods. We have used the Multi-Unit Spectroscopic Explorer (MUSE) optical integral field spectrograph at the Very Large Telescope (VLT) on Cerro Paranal to obtain deep observations of SNR 1E 0102 in the Small Magellanic Cloud. Our observations cover the entire extent of the remnant with a seeing limited spatial resolution of 0.7 0.2 pc at the distance of 1E 0102. Results. Our MUSE observations unambiguously reveal the presence of [Fe XIV] and [Fe XI] emission in 1E 0102. The emission largely arises from a thin, partial ring of filaments surrounding the fast-moving O-rich ejecta in the system. The brightest [Fe XIV] and [Fe XI] emission is found along the eastern and north-western sides of 1E 0102, where shocks are driven into denser ISM material, while fainter emission along the northern edge reveals the location of the forward shock in lower-density gas, possibly the relic stellar wind cavity. Modeling the eastern shocks and the photoionization precursor surrounding 1E 0102, we derive a pre-shock density n_H = (7.4 ± 1.5) cm^-3, and a shock velocity 330 km s^-1<v_s< 350 km s^-1.