Dense Molecular Clumps associated with the LMC Supergiant Shells LMC 4
  \& LMC 5
  We investigate the effects of Supergiant Shells (SGSs) and their interaction
on dense molecular clumps by observing the Large Magellanic Cloud (LMC) star
forming regions N48 and N49, which are located between two SGSs, LMC 4 and LMC
5. $^{12}$CO ($J$=3-2, 1-0) and $^{13}$CO ($J$=1-0) observations with the ASTE
and Mopra telescopes have been carried out towards these regions. A clumpy
distribution of dense molecular clumps is revealed with 7 pc spatial
resolution. Large velocity gradient analysis shows that the molecular hydrogen
densities ($n({\rm H}_2)$) of the clumps are distributed from low to high
density ($10^3$-$10^5$ cm$^{-3}$) and their kinetic temperatures ($T_{\rm
kin}$) are typically high (greater than $50$ K). These clumps seem to be in the
early stages of star formation, as also indicated from the distribution of
H$\alpha$, young stellar object candidates, and IR emission. We found that the
N48 region is located in the high column density HI envelope at the interface
of the two SGSs and the star formation is relatively evolved, whereas the N49
region is associated with LMC 5 alone and the star formation is quiet. The
clumps in the N48 region typically show high $n({\rm H}_2)$ and $T_{\rm kin}$,
which are as dense and warm as the clumps in LMC massive cluster-forming areas
(30 Dor, N159). These results suggest that the large-scale structure of the
SGSs, especially the interaction of two SGSs, works efficiently on the
formation of dense molecular clumps and stars.
