paper

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

arXiv:2108.10519 · doi:10.1051/0004-6361/202141804

Abstract

We mapped the kinetic temperature structure of two massive star-forming regions, N113 and N159W, in the Large Magellanic Cloud (LMC). We have used $\sim$ 1\hbox{ $.^{''}$ }6\,( $\sim$ 0.4\,pc) resolution measurements of the para-H $_{2}$ CO\, $J_{K_{a} K_{c}}$ \,=\,3 $_{03}$ --2 $_{02}$ , 3 $_{22}$ --2 $_{21}$ , and 3 $_{21}$ --2 $_{20}$ transitions near 218.5\,GHz to constrain RADEX non-LTE models of the physical conditions. The gas kinetic temperatures derived from the para-H $_{2}$ CO 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-H $_{2}$ CO agree with those of the 1.3\,mm dust and \emph{Spitzer}\,8.0\, $I^¼$ m emission, but do not significantly correlate with the H $I^\pm$ emission. The high kinetic temperatures ( $T_{kin}$ \, $≳$ \,50\,K) of the dense gas traced by para-H $_{2}$ CO appear to be correlated with the embedded infrared sources inside the clouds and/or YSOs in the N113 and N159W regions. The lower temperatures ( $T_{kin}$ \, $<$ \,50\,K) are measured at the outskirts of the H $_{2}$ CO-bearing distributions of both N113 and N159W. It seems that the kinetic temperatures of the dense gas traced by para-H $_{2}$ CO are weakly affected by the external sources of the H $I^\pm$ emission. The non-thermal velocity dispersions of para-H $_{2}$ CO are well correlated with the gas kinetic temperatures in the N113 region, implying that the higher kinetic temperature traced by para-H $_{2}$ CO is related to turbulence on a $\sim$ 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.

Accepted for publication in A&A