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 $^{12}$CO($J$ = 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 $\sim$10-15 pc and $\sim$1000-3000
$M_{\odot}$, 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
$^{12}$CO($J$ = 3-2) / $^{12}$CO($J$ = 1-0) $> 1.2$, which are not attributable
to any identified internal infrared sources or high-mass stars. The HI 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 HI clouds within the wind-blown cavity at
$V_\mathrm{LSR} = 117.1$-122.5 km s$^{-1}$ are to be associated with the SNR.
The X-ray spectroscopy reveals the dynamical age of $26000^{+1000}_{-2000}$ yr
and the progenitor mass of $\gtrsim 30$ $M_{\odot}$, 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 datasets of the Atacama Large Millimeter/submillimeter Array; the
kinematic temperature is $72^{+50}_{-37}$ K and the number density of molecular
hydrogen is $1500^{+600}_{-300}$ cm$^{-3}$. The next generation of $\gamma$-ray
observations will allow us to study the pion-decay $\gamma$-rays from the
molecular clouds in the SMC SNR.
