Formation of High-Mass stars in an isolated environment in the Large
  Magellanic Cloud
  The aim of this study is to characterize the distribution and basic
properties of the natal gas associated with high-mass young stellar objects
(YSOs) in isolated environments in the Large Magellanic Cloud (LMC). High-mass
stars usually form in Giant Molecular Clouds (GMCs) as part of a young stellar
cluster, but some OB stars are observed far from GMCs. By examining the spatial
coincidence between the high-mass YSOs and 12CO (J = 1-0) emission detected by
NANTEN and Mopra observations, we selected ten high-mass YSOs that are located
away from any of the NANTEN clouds but are detected by the Mopra pointed
observations. The ALMA observations revealed that a compact molecular cloud
whose mass is a few thousand solar masses or smaller is associated with the
high-mass YSOs, which indicates that these compact clouds are the sites of
high-mass star formation. The high-density and high-temperature throughout the
clouds are explained by the severe photodissociation of CO due to the lower
metallicity than in the Galaxy. The star formation efficiency ranges from
several to as high as ~ 40%, indicating efficient star formation in these
environments. The enhanced turbulence may be a cause of the efficient star
formation therein, as judged from the gas velocity information and the
association with the lower density gas.
