A MULTIWAVELENGTH STUDY OF THE SUPERNOVA REMNANT N49 IN THE LARGE MAGELLANIC CLOUD

Using the 2.5 m du Pont telescope at Las Campanas, the International Ultraviolet Explorer satellite, and archival high-resolution imager X-ray data from the Einstein Observatory, we present a detailed imaging and spectroscopic study of the supernova remnant (SNR) N49 in the Large Magellanic Cloud. Although the X-ray and optical morphology of N49 are similar in the sense that the SNR is brightest in the southeast, the SNR is more circular and extended in the X-ray map, and individual features in the optical and X-ray images do not in general correspond with one another. The asymmetry of the optical image and the relatively high X-ray and optical luminosity of this remnant both arise from its interaction with an extended dense cloud to the southeast seen in CO emission. The optical spectra reveal clear evidence of reddening variations on spatial scales as small as approximately 2" over the face of the SNR. Ultraviolet line emission is associated primarily with the bright optical filaments, and we measure the total luminosity of N49 in several optical and UV lines. A combined analysis of IUE and optical spectra indicates a range of radiative shock velocities. The bulk of the observed emission emanates from shocks with velocities less-than-or-equal-to 140 km s-1, although echelle data indicate that faint shocks greater-than-or-equal-to 200 km s-1 must be present. Upon modeling the spectrum, we find that a power-law velocity distribution corresponding to 40 km s-1 less-than-or-equal-to V(s) less-than-or-equal-to 270 km s-1 provides a good match, with the bulk of the emission arising from the slower shocks. Preshock densities of 20-940 cm-3 and postshock nonthermal pressure support are required to account for both the total optical and UV luminosities and the densities inferred from the [S II] doublet. We derive improved elemental abundances for N49. We conclude by discussing implications for the interstellar medium surrounding N49. We develop a model invoking a Sedov solution in which the main blast wave also encounters large clouds. For this model, we demonstrate that the energetics of N49's evolution as a whole and blast wave/cloud interactions on a smaller scale are self-consistent.