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 similar to 1.'' 6 (similar to 0.4 pc) resolution measurements of the para-H2CO J(Ka)K(c) JKaKc = 3(03)-2(02), 3(22)-2(21), and 3(21)-2(20) 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 3(22)-2(21)/3(03)-2(02) and 3(21)-2(20)/3(03)-2(02) 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 mu m emission, but they do not significantly correlate with the H alpha emission. The high kinetic temperatures (T-kin greater than or similar to 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 H alpha 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 similar to 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.

Automated summary

The study on the kinetic temperature structure of two massive star-forming regions in the Large Magellanic Cloud found that the dense gas's kinetic temperature is influenced by embedded infrared sources and/or young stellar objects. Lower temperatures were measured at the outskirts of H2CO-traced dense gas distributions, while turbulence may be correlated with higher kinetic temperatures.