First Detection of Ammonia in the Large Magellanic Cloud: The Kinetic
  Temperature of Dense Molecular Cores in N159W
  The first detection of ammonia (NH3) is reported from the Magellanic Clouds.
Using the Australia Telescope Compact Array, we present a targeted search for
the (J,K) = (1,1) and (2,2) inversion lines towards seven prominent
star-forming regions in the Large Magellanic Cloud (LMC). Both lines are
detected in the massive star-forming region N159W, which is located in the
peculiar molecular ridge south of 30 Doradus, a site of extreme star formation
strongly influenced by an interaction with the Milky Way halo. Using the
ammonia lines, we derive a kinetic temperature of ~16K, which is 2-3 times
below the previously derived dust temperature. The ammonia column density,
averaged over ~17" is ~6x10^{12} cm^{-2} <1.5x10^{13} cm^{-2} over 9" in the
other six sources) and we derive an ammonia abundance of ~4x10^{-10} with
respect to molecular hydrogen. This fractional abundance is 1.5-5 orders of
magnitude below those observed in Galactic star-forming regions. The nitrogen
abundance in the LMC (~10% solar) and the high UV flux, which can
photo-dissociate the particularly fragile NH3 molecule, must both contribute to
the low fractional NH3 abundance, and we likely only see the molecule in an
ensemble of the densest, best shielded cores of the LMC.
