Kinetic temperature of massive star forming molecular clumps measured
  with formaldehyde. II. The Large Magellanic Cloud
  The Large Magellanic Cloud (LMC), the closest star forming galaxy with low
metallicity, provides an ideal laboratory to study star formation in such an
environment. The classical dense molecular gas thermometer NH3 is rarely
available in a low metallicity environment because of photoionization and a
lack of nitrogen atoms. Our goal is to directly measure the gas kinetic
temperature with formaldehyde toward six star-forming regions in the LMC. Three
rotational transitions of para-H2CO near 218 GHz were observed with the APEX
12m telescope toward six star forming regions in the LMC. Those data are
complemented by C18O 2-1 spectra. Using non-LTE modeling with RADEX, we derive
the gas kinetic temperature and spatial density, using as constraints the
measured para-H2CO 321-220/303-202 and para-H2CO 303-202/C18O 2-1 ratios.
Excluding the quiescent cloud N159S, where only one para-H2CO line could be
detected, the gas kinetic temperatures derived from the preferred para-H2CO
321-220/303-202 line ratios range from 35 to 63 K with an average of 47 K.
Spatial densities of the gas derived from the paraH2CO 303-202/C18O 2-1 line
ratios yield 0.4-2.9x10^5 cm^-3 with an average of 1.5x10^5 cm^-3. Temperatures
derived from the para-H2CO line ratio are similar to those obtained with the
same method from Galactic star forming regions and agree with results derived
from CO in the dense regions of the LMC. A comparison of kinetic temperatures
derived from para-H2CO with those from the dust also shows good agreement. This
suggests that the dust and para-H2CO are well mixed in the studied star forming
regions. A correlation between the gas kinetic temperatures derived from
para-H2CO and infrared luminosity, represented by the 250um flux, suggests that
the kinetic temperatures traced by para-H2CO are correlated with the ongoing
massive star formation in the LMC.
