Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde. IV. The ALMA view of N113 and N159W in the LMC

We mapped the kinetic temperature structure of two massive star-forming regions, N113 and N159W, in the Large Magellanic Cloud (LMC). We have used ~1.′′6 (~0.4 pc) resolution measurements of the para-H₂CO J_KaKc = 3₀₃-2₀₂, 3₂₂-2₂₁, and 3₂₁-2₂₀ transitions near 218.5 GHz to constrain RADEX non local thermodynamic equilibrium models of the physical conditions. The gas kinetic temperatures derived from the para-H₂CO line ratios 3₂₂-2₂₁/3₀₃-2₀₂ and 3₂₁-2₂₀/3₀₃-2₀₂ range from 28 to 105 K in N113 and 29 to 68 K in N159W. Distributions of the dense gas traced by para-H₂CO agree with those of the 1.3 mm dust and Spitzer 8.0 μm emission, but they do not significantly correlate with the Hα emission. The high kinetic temperatures (T_kin ≳ 50 K) of the dense gas traced by para-H₂CO appear to be correlated with the embedded infrared sources inside the clouds and/or young stellar objects in the N113 and N159W regions. The lower temperatures (T_kin < 50 K) were measured at the outskirts of the H₂CO-bearing distributions of both N113 and N159W. It seems that the kinetic temperatures of the dense gas traced by para-H₂CO are weakly affected by the external sources of the Hα emission. The non thermal velocity dispersions of para-H₂CO are well correlated with the gas kinetic temperatures in the N113 region, implying that the higher kinetic temperature traced by para-H₂CO is related to turbulence on a ~0.4 pc scale. The dense gas heating appears to be dominated by internal star formation activity, radiation, and/or turbulence. It seems that the mechanism heating the dense gas of the star-forming regions in the LMC is consistent with that in Galactic massive star-forming regions located in the Galactic plane.

The reduced datacubes are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/655/A12