Supernova Remnants Associated with Molecular Clouds in the Large Magellanic Cloud

We used the Swedish-ESO Submillimeter Telescope (SEST) to search for COemission associated with three supernova remnants (SNRs) in the LargeMagellanic Cloud: N49, N132D, and N23. Observations were carried out in theJ=2-1 rotational transition of CO (230.5 GHz) where the half power beamwidth ofthe SEST is 23". Molecular clouds were discovered near N49 and N132D; no COemission was discovered in the region we mapped near N23. The N49 cloud has apeak line temperature of 0.75 K, spatial scale of ~7 pc and virial mass of~30,000 solar masses. The N132D cloud is brighter with a peak temperature of 5K; it is also larger ~22 pc and considerably more massive 200,000 solar masses.The velocities derived for the clouds near N49 and N132D, +286.0 km/s and+264.0 km/s, agree well with the previously known velocities of the associatedSNRs: +286 km/s and +268 km/s, respectively. ROSAT X-ray images show that theambient density into which the remnants are expanding appears to besignificantly increased in the direction of the clouds. Taken together theseobservations indicate a physical association between the remnants and theirrespective, presumably natal, molecular clouds. The association of N49 andN132D with dense regions of molecular material means that both were likelyproducts of short-lived progenitors that exploded as core-collapse supernovae.Comment: 26 pages, including 9 postscript figs, LaTeX (includes aaspp.sty), accepted by Ap.J. for vol 480, May 10, 199