1999ApJ...511..262X

High-resolution (10 km.s^–1) [N II] echelle spectra, sampled every 13" in a 6'x6' region around SN 1987A were obtained on the CTIO 4 m telescope. The map shows a complicated velocity structure consistent with that reported previously for the interstellar medium (ISM). Three components, V_hel=265, 277, and 285 km.s^–1 were identified as N157C (or the R1170 complex: see an earlier paper of Xu, Crotts, & Kunkel). The radius of this large superbubble was found to expand at 10 km.s^–1, with a lifetime of 6x10⁶ yr and a total energy of 3x10⁵¹ ergs determined from its radius and velocity according to superbubble theory. The V_hel=235 km.s^–1 component corresponds to the near side of the 600 pc giant superbubble reported earlier. This bubble is over 10⁷ years old, and has blown out of the Large Magellanic Cloud disk. Two other components, V_hel=255 and 245 km.s^–1 are identified as the inner major light echo ring (a double-shell structure) at about 130 pc in front of SN 1987A. There are also two high-velocity components, 300 and 313 km.s^–1, which are possibly the far side of a superbubble in which SN 1987A exploded. We also noticed that there are two components, at 279 and 301 km.s^–1, within 20" of SN 1987A. These structures are probably due to the emission from the progenitor star's red supergiant wind. We find that the time it took the SN 1987A progenitor to move to the current location 300 pc behind N157C is comparable to the age of N157C as well as that of the progenitor itself.