Detection of a hot molecular core in the Large Magellanic Cloud with
  ALMA
  We report the first detection of a hot molecular core outside our Galaxy
based on radio observations with ALMA toward a high-mass young stellar object
(YSO) in a nearby low metallicity galaxy, the Large Magellanic Cloud (LMC).
Molecular emission lines of CO, C17O, HCO+, H13CO+, H2CO, NO, SiO, H2CS, 33SO,
32SO2, 34SO2, and 33SO2 are detected from a compact region (0.1 pc) associated
with a high-mass YSO, ST11. The temperature of molecular gas is estimated to be
higher than 100 K based on rotation diagram analysis of SO2 and 34SO2 lines.
The compact source size, warm gas temperature, high density, and rich molecular
lines around a high-mass protostar suggest that ST11 is associated with a hot
molecular core. We find that the molecular abundances of the LMC hot core are
significantly different from those of Galactic hot cores. The abundances of
CH3OH, H2CO, and HNCO are remarkably lower compared with Galactic hot cores by
at least 1-3 orders of magnitude. We suggest that these abundances are
characterized by the deficiency of molecules whose formation requires the
hydrogenation of CO on grain surfaces. In contrast, NO shows a high abundance
in ST11 despite the notably low abundance of nitrogen in the LMC. A multitude
of SO2 and its isotopologue line detections in ST11 imply that SO2 can be a key
molecular tracer of hot core chemistry in metal-poor environments. Furthermore,
we find molecular outflows around the hot core, which is the second detection
of an extragalactic protostellar outflow. In this paper, we discuss physical
and chemical characteristics of a hot molecular core in the low metallicity
environment.
