Chemistry and physics of a low-metallicity hot core in the Large
  Magellanic Cloud
  We present the results of 0.1-pc-scale observations in 250 GHz and 350GHz
towards a newly-discovered hot molecular core in a nearby low-metallicity
galaxy, the Large Magellanic Cloud (LMC), with the Atacama Large
Millimeter/submillimeter Array. A variety of C/N/O/Si/S-bearing molecules are
detected towards the high-mass young stellar object, ST16. A rotating
protostellar envelope is for the first time detected outside our Galaxy by SO2
and 34SO lines. An outflow cavity is traced by CCH and CN. The isotope
abundance of sulfur in the source is estimated to be 32S/34S = 17 and 32S/33S =
53 based on SO, SO2, and CS isotopologues, suggesting that both 34S and 33S are
overabundant in the LMC. Rotation diagram analyses show that the source is
associated with hot gas (>100K) traced by high-excitation lines of CH3OH and
SO2, as well as warm gas (~50K) traced by CH3OH, SO2, 34SO, OCS, CH3CN lines. A
comparison of molecular abundances between LMC and Galactic hot cores suggests
that organic molecules (e.g., CH3OH, a classical hot core tracer) show a large
abundance variation in low metallicity, where the present source is classified
into an organic-poor hot core. Our astrochemical simulations suggest that
different grain temperature during the initial ice-forming stage would
contribute to the chemical differentiation. In contrast, SO2 shows similar
abundances within all the known LMC hot cores and the typical abundance roughly
scales with the LMC's metallicity. Nitrogen-bearing molecules are generally
less abundant in LMC hot cores, except for NO. The present results suggest that
chemical compositions of hot cores do not always simply scale with the
metallicity.
