Discovery of Shocked Molecular Clouds Associated with the Shell-type Supernova Remnant RX J0046.5-7308 in the Small Magellanic Cloud

RX J0046.5-7308 is a shell-type supernova remnant (SNR) in the Small Magellanic Cloud (SMC). We carried out new (CO)-C-12(J = 1-0, 3-2) observations toward the SNR using Mopra and the Atacama Submillimeter Telescope Experiment. We found eight molecular clouds (A-H) along the X-ray shell of the SNR. The typical cloud size and mass are similar to 10-15. pc and similar to 1000-3000. M-circle dot, respectively. The X-ray shell is slightly deformed and has the brightest peak in the southwestern shell where two molecular clouds A and B are located. The four molecular clouds A, B, F, and G have high intensity ratios of (CO)-C-12(J = 3-2)/(CO)-C-12(J = 1-0) > 1.2, which are not attributable to any identified internal infrared sources or high-mass stars. The H I cavity and its expanding motion are found toward the SNR, which are likely created by strong stellar winds from a massive progenitor. We suggest that the molecular clouds A-D, F, and G and H I clouds within the wind-blown cavity at V-LSR = 117.1-122.5 km s(-1) are associated with the SNR. The X-ray spectroscopy reveals the dynamical age of 26000(-2000)(+1000) yr and the progenitor mass of greater than or similar to 30M(circle dot), which is also consistent with the proposed scenario. We determine physical conditions of the giant molecular cloud LIRS 36A using the large velocity gradient analysis with archival data sets of the Atacama Large Millimeter/submillimeter Array; the kinematic temperature is 72(-37)(+50) K and the number density of molecular hydrogen is 1500(-300)(+600) cm(-3). The next generation of gamma-ray observations will allow us to study the pion-decay.-rays from the molecular clouds in the SMC SNR.